Squashed commit of the following:

commit 21309f2c
Merge: f69672e8 7a2e492e
Author: Manuel Kocher <manuel.kocher@tugraz.at>
Date:   Thu May 12 14:16:56 2022 +0200

    Merge branch 'master' into dbp-translation-component

commit f69672e8
Author: Manuel Kocher <manuel.kocher@tugraz.at>
Date:   Thu May 12 13:48:10 2022 +0200

    Remove unnecessary en translation text

commit 6d0df984
Author: Manuel Kocher <manuel.kocher@tugraz.at>
Date:   Thu May 12 13:36:45 2022 +0200

    Remove unnecessary imports and minor refactor

commit 6496d910
Author: Manuel Kocher <manuel.kocher@tugraz.at>
Date:   Thu May 12 13:24:51 2022 +0200

    Add lang-File attribute to README

commit 7a528144
Author: Manuel Kocher <manuel.kocher@tugraz.at>
Date:   Thu May 12 13:17:40 2022 +0200

    Add dbp-translation component and include it in showcase

This was used to create HTML elements for a shadow dom, but this
is now provided by the scoped-elements mixin via this.createScopedElement().

One way to handle this is enough, so remove this again.
All users have been ported already.

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.