.github/workflows distributed with package

[wilbowma]

I happened to notice that the .github folder gets installed with the package. This is kind of a minor bug, but doesn't seem like it should get installed.

> ls -a /usr/local/Cellar/minimal-racket/8.7/share/racket/pkgs/metapict/
.          ..         .github    README.txt info.rkt   metapict
> ls -a /usr/local/Cellar/minimal-racket/8.7/share/racket/pkgs/metapict/.github/workflows/
.        ..       push.yml