Updates CF deps and converts RSS pattern into an include

- Updated to use cf-core
- Fixes any updated class names and mixin names and removes duplicate patterns that were moved over to cf-core.
- Converts RSS pattern into a reusable include.
cf-expandables updated to add a transparent background and zero padding to `.expandable_target`. These styles are overriding the button styles. As a temporary fix I just made a custom class in cfgov-refresh.

If you're cool with it then I'll update the static pages as well.