Push Theme Changes

1. Check which themes have local changes:

   gon push

2. Push a frontend theme:

   gon push --theme mysite -m "fix: header layout"

3. Push an admin theme:

   gon push --theme polygon --theme-type=admin -m "fix: sidebar nav"

4. Push with a version tag:

   gon push --theme mysite --tag=v1.2.0 -m "release: v1.2.0"