Add categories to pull screen - 2

[kirtangajjar]

Description of the Change

Add categories to the pull screen. This is part 2 of 2 of this issue. This PR filters posts by categories.

Closes #428

How to test the Change

1. Open post pull screen
2. You should be able to see post categories in the filter.
3. Select a category and filter. The posts should be filtered by categories.
4. Pull the posts and verify only posts from that category have been pulled.
5. Verify it on both internal and external connections.
6. Verify it in conjunction with post type filter as well.

Changelog Entry

Added - Category filter in pull screen

Credits

Props @kirtangajjar

Checklist:

• [x] I agree to follow this project's Code of Conduct.
• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my change.
• [ ] All new and existing tests pass.