BREAKING CHANGE: Rename `@material/web/<component>/lib` to `@material/web/<component>/internal`. Prefer not using internal files.
PiperOrigin-RevId: 550633216
In particular, this allows external build tools like Rollup and @web/dev-server to understand imports of Lit, which is configured to require the ".js" extension via its export conditions (so that Lit import maps can remain minimal).
PiperOrigin-RevId: 469772992