fix: manually ignore bazel-* directories to make using custom Bazel b…

…uilds easier

Normally, Bazel will ignore its convenience symlinks, so putting them
in the .bazelignore file isn't necessary. However, when
`--output_user_root` is set, which is beneficial to set when using
different Bazel versions (it preserves the analysis cache between
versions), the symlinks aren't ignored. Putting them in the bazelignore
file fixes this.

.bazelignore

@@ -0,0 +1,8 @@
+# Normally these are ignored, but if you're using a custom
+# build of Bazel with a custom --output_user_root value, Bazel
+# tries to follow the symlinks of the other builds and finds
+# the WORKSPACE, BUILD, etc files and tries to build them.
+bazel-rules_python
+bazel-bin
+bazel-out
+bazel-testlogs