dillon1000/react

[DevTools] Make Toggle hover state more visible (#32914)

This change adds a background color to Toggles to make them easier to
see. This is especially important when DevTools are not in focus, and
it's harder to see.

Test plan:
1. `yarn build:chrome:local`
2. Inspect components 
3. Hover over "Select an Element in page to inspect it"
4. Observe background change