third_party/rust: initialize, add mdbook

As we want to use [mdbook](https://github.com/rust-lang/mdBook) to build
documentation, we now have to pull it into the monorepo, alongside
support for Rust in general.

Testing plan: bazel run //third_party/rust:cargo_bin_mdbook. The CI
should also pick this up now.

Change-Id: I6cf5d02d926bb0de61a5c882828accd35f3a1076
Reviewed-on: https://review.monogon.dev/c/monogon/+/201
Reviewed-by: Leopold Schabel <leo@nexantic.com>
diff --git a/third_party/rust/cargo/remote/BUILD.tokio-0.2.25.bazel b/third_party/rust/cargo/remote/BUILD.tokio-0.2.25.bazel
new file mode 100644
index 0000000..1d76ac8
--- /dev/null
+++ b/third_party/rust/cargo/remote/BUILD.tokio-0.2.25.bazel
@@ -0,0 +1,289 @@
+"""
+@generated
+cargo-raze crate build file.
+
+DO NOT EDIT! Replaced on runs of cargo-raze
+"""
+
+# buildifier: disable=load
+load("@bazel_skylib//lib:selects.bzl", "selects")
+
+# buildifier: disable=load
+load(
+    "@rules_rust//rust:rust.bzl",
+    "rust_binary",
+    "rust_library",
+    "rust_test",
+)
+
+package(default_visibility = [
+    # Public for visibility by "@raze__crate__version//" targets.
+    #
+    # Prefer access through "//third_party/rust/cargo", which limits external
+    # visibility to explicit Cargo.toml dependencies.
+    "//visibility:public",
+])
+
+licenses([
+    "notice",  # MIT from expression "MIT"
+])
+
+# Generated Targets
+
+rust_library(
+    name = "tokio",
+    srcs = glob(["**/*.rs"]),
+    aliases = {
+    },
+    crate_features = [
+        "blocking",
+        "default",
+        "fnv",
+        "fs",
+        "futures-core",
+        "io-driver",
+        "io-util",
+        "iovec",
+        "lazy_static",
+        "macros",
+        "memchr",
+        "mio",
+        "rt-core",
+        "slab",
+        "stream",
+        "sync",
+        "tcp",
+        "time",
+        "tokio-macros",
+    ],
+    crate_root = "src/lib.rs",
+    crate_type = "lib",
+    data = [],
+    edition = "2018",
+    proc_macro_deps = [
+        "@raze__tokio_macros__0_2_6//:tokio_macros",
+    ],
+    rustc_flags = [
+        "--cap-lints=allow",
+    ],
+    tags = [
+        "cargo-raze",
+        "manual",
+    ],
+    version = "0.2.25",
+    # buildifier: leave-alone
+    deps = [
+        "@raze__bytes__0_5_6//:bytes",
+        "@raze__fnv__1_0_7//:fnv",
+        "@raze__futures_core__0_3_15//:futures_core",
+        "@raze__iovec__0_1_4//:iovec",
+        "@raze__lazy_static__1_4_0//:lazy_static",
+        "@raze__memchr__2_4_0//:memchr",
+        "@raze__mio__0_6_23//:mio",
+        "@raze__pin_project_lite__0_1_12//:pin_project_lite",
+        "@raze__slab__0_4_3//:slab",
+    ] + selects.with_or({
+        # cfg(unix)
+        (
+            "@rules_rust//rust/platform:x86_64-unknown-linux-gnu",
+        ): [
+        ],
+        "//conditions:default": [],
+    }),
+)
+
+# Unsupported target "_require_full" with type "test" omitted
+
+# Unsupported target "async_send_sync" with type "test" omitted
+
+# Unsupported target "buffered" with type "test" omitted
+
+# Unsupported target "fs" with type "test" omitted
+
+# Unsupported target "fs_copy" with type "test" omitted
+
+# Unsupported target "fs_dir" with type "test" omitted
+
+# Unsupported target "fs_file" with type "test" omitted
+
+# Unsupported target "fs_file_mocked" with type "test" omitted
+
+# Unsupported target "fs_link" with type "test" omitted
+
+# Unsupported target "io_async_read" with type "test" omitted
+
+# Unsupported target "io_chain" with type "test" omitted
+
+# Unsupported target "io_copy" with type "test" omitted
+
+# Unsupported target "io_driver" with type "test" omitted
+
+# Unsupported target "io_driver_drop" with type "test" omitted
+
+# Unsupported target "io_lines" with type "test" omitted
+
+# Unsupported target "io_mem_stream" with type "test" omitted
+
+# Unsupported target "io_read" with type "test" omitted
+
+# Unsupported target "io_read_exact" with type "test" omitted
+
+# Unsupported target "io_read_line" with type "test" omitted
+
+# Unsupported target "io_read_to_end" with type "test" omitted
+
+# Unsupported target "io_read_to_string" with type "test" omitted
+
+# Unsupported target "io_read_until" with type "test" omitted
+
+# Unsupported target "io_reader_stream" with type "test" omitted
+
+# Unsupported target "io_split" with type "test" omitted
+
+# Unsupported target "io_take" with type "test" omitted
+
+# Unsupported target "io_write" with type "test" omitted
+
+# Unsupported target "io_write_all" with type "test" omitted
+
+# Unsupported target "io_write_int" with type "test" omitted
+
+# Unsupported target "macros_join" with type "test" omitted
+
+# Unsupported target "macros_pin" with type "test" omitted
+
+# Unsupported target "macros_select" with type "test" omitted
+
+# Unsupported target "macros_test" with type "test" omitted
+
+# Unsupported target "macros_try_join" with type "test" omitted
+
+# Unsupported target "net_bind_resource" with type "test" omitted
+
+# Unsupported target "net_lookup_host" with type "test" omitted
+
+# Unsupported target "no_rt" with type "test" omitted
+
+# Unsupported target "process_issue_2174" with type "test" omitted
+
+# Unsupported target "process_issue_42" with type "test" omitted
+
+# Unsupported target "process_kill_on_drop" with type "test" omitted
+
+# Unsupported target "process_smoke" with type "test" omitted
+
+# Unsupported target "rt_basic" with type "test" omitted
+
+# Unsupported target "rt_common" with type "test" omitted
+
+# Unsupported target "rt_threaded" with type "test" omitted
+
+# Unsupported target "signal_ctrl_c" with type "test" omitted
+
+# Unsupported target "signal_drop_recv" with type "test" omitted
+
+# Unsupported target "signal_drop_rt" with type "test" omitted
+
+# Unsupported target "signal_drop_signal" with type "test" omitted
+
+# Unsupported target "signal_multi_rt" with type "test" omitted
+
+# Unsupported target "signal_no_rt" with type "test" omitted
+
+# Unsupported target "signal_notify_both" with type "test" omitted
+
+# Unsupported target "signal_twice" with type "test" omitted
+
+# Unsupported target "signal_usr1" with type "test" omitted
+
+# Unsupported target "stream_chain" with type "test" omitted
+
+# Unsupported target "stream_collect" with type "test" omitted
+
+# Unsupported target "stream_empty" with type "test" omitted
+
+# Unsupported target "stream_fuse" with type "test" omitted
+
+# Unsupported target "stream_iter" with type "test" omitted
+
+# Unsupported target "stream_merge" with type "test" omitted
+
+# Unsupported target "stream_once" with type "test" omitted
+
+# Unsupported target "stream_pending" with type "test" omitted
+
+# Unsupported target "stream_reader" with type "test" omitted
+
+# Unsupported target "stream_stream_map" with type "test" omitted
+
+# Unsupported target "stream_timeout" with type "test" omitted
+
+# Unsupported target "sync_barrier" with type "test" omitted
+
+# Unsupported target "sync_broadcast" with type "test" omitted
+
+# Unsupported target "sync_cancellation_token" with type "test" omitted
+
+# Unsupported target "sync_errors" with type "test" omitted
+
+# Unsupported target "sync_mpsc" with type "test" omitted
+
+# Unsupported target "sync_mutex" with type "test" omitted
+
+# Unsupported target "sync_mutex_owned" with type "test" omitted
+
+# Unsupported target "sync_notify" with type "test" omitted
+
+# Unsupported target "sync_oneshot" with type "test" omitted
+
+# Unsupported target "sync_rwlock" with type "test" omitted
+
+# Unsupported target "sync_semaphore" with type "test" omitted
+
+# Unsupported target "sync_semaphore_owned" with type "test" omitted
+
+# Unsupported target "sync_watch" with type "test" omitted
+
+# Unsupported target "task_blocking" with type "test" omitted
+
+# Unsupported target "task_local" with type "test" omitted
+
+# Unsupported target "task_local_set" with type "test" omitted
+
+# Unsupported target "tcp_accept" with type "test" omitted
+
+# Unsupported target "tcp_connect" with type "test" omitted
+
+# Unsupported target "tcp_echo" with type "test" omitted
+
+# Unsupported target "tcp_into_split" with type "test" omitted
+
+# Unsupported target "tcp_peek" with type "test" omitted
+
+# Unsupported target "tcp_shutdown" with type "test" omitted
+
+# Unsupported target "tcp_split" with type "test" omitted
+
+# Unsupported target "test_clock" with type "test" omitted
+
+# Unsupported target "time_delay" with type "test" omitted
+
+# Unsupported target "time_delay_queue" with type "test" omitted
+
+# Unsupported target "time_interval" with type "test" omitted
+
+# Unsupported target "time_rt" with type "test" omitted
+
+# Unsupported target "time_throttle" with type "test" omitted
+
+# Unsupported target "time_timeout" with type "test" omitted
+
+# Unsupported target "udp" with type "test" omitted
+
+# Unsupported target "uds_cred" with type "test" omitted
+
+# Unsupported target "uds_datagram" with type "test" omitted
+
+# Unsupported target "uds_split" with type "test" omitted
+
+# Unsupported target "uds_stream" with type "test" omitted