It has new API which we want to use.

Newest Ubuntu switched Firefox to a snap, which breaks karma.

Try to use playwright to download and cache firefox/chromium
and use those for karma.

Compared to puppeteer where we did this some time ago this caches
the browsers globally, and only downloads them when we start the tests.

This reverts commit 6324718b.

This reverts commit 3716524b.

Just change all imports and dependencies.

No longer needs babel, but requries an alpha version of the typescript plugin
for eslint 8 support

This has proper support for rollup while providing the same API.

This is what open-wc recommends now and uses in their @open-wc/testing package

Versions: Lit-Element to 2.4.0 and Lit-HTML to 1.3.0

This fixes a typescript problem and allows us to enable type checking
in the typescript-example package (by removing the ts-nocheck comment)

This is all very basic, building works, testing works,
but there are type checking errors which I don't know how
to fix.

Improvements welcome.

See #41