This PR fixes a bug where dark mode would not immediately cause shapes
to update their colors. Previously, we got the current theme during
render but not in a way that hooked into the change. In this update, we
hook into the change. We also pass the change down to shape fills as
props rather than getting the theme from deeper down.
### Change Type
- [x] `patch`
### Test Plan
1. Use dark mode.
2. Switch colors
### Release Notes
- [fix] dark mode colors not updating
