general: add .unity-bin to gitignore
general: add .unity-bin to gitignore

When using unity with a version of /path/to/cue, the .unity-bin
directory is used as the cache of the compiled target binary. This
therefore needs to be added to gitignore to avoid accidentally adding
such binaries to git.

Change-Id: I004f0f4c546e83add1c3b17d362fe48d248b0ecc
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/8941
Reviewed-by: CUE cueckoo <0f32a827c9a5f00281f936ac78b5ef3ba80a954c@gmail.com>
Reviewed-by: Paul Jolly <a027184a55211cd23e3f3094f1fdc728df5e0500@myitcv.org.uk>

cuelang/cue