gitignore: add vim swp files

Change-Id: I09a1f8d314fd79464fd355779f6b51d0c1302854
Reviewed-on: https://review.monogon.dev/c/monogon/+/29
Reviewed-by: Leopold Schabel <leo@nexantic.com>
diff --git a/.gitignore b/.gitignore
index ac51a05..f03764d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 bazel-*
+*swp