Support propagating theme from Chrome DevTools frontend, the field is
optional.
Next step, which is out of scope of this project and general improvement
for React DevTools: teach RDT to listen to theme changes and if the
theme preference is set to `auto` in settings, update the theme
accordingly with the browser devtools.
## Summary
Stacked on https://github.com/facebook/react/pull/28552. Review only the
[last commit at the
top](c69952f1bf).
These changes add new package `react-devtools-fusebox`, which is the
entrypoint for the RDT Frontend, which will be used in Chrome DevTools
panel. The main differences from other frontend shells (extension,
standalone) are:
1. This package builds scripts in ESM format, this is required by Chrome
DevTools, see webpack config:
c69952f1bf/packages/react-devtools-fusebox/webpack.config.frontend.js (L50-L52)
2. The build includes styles in a separate `.css` file, which is
required for Chrome DevTools: styles are loaded lazily once panel is
mounted.
