Add new theme style (github-compact)

[bijink]

All Submissions

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

New Feature Submissions

1. Does your submission pass tests?
2. Have you lint your code locally prior to submission?

Changes to Core Features

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?

New theme feature

• Compatible with github default dark and light themes