This is used in various packages, so clean it up and add it
to rollup.utils.js.

Use "language" instead of "lang" because "lang" seems to be handled specially in html elements (dbp/apps/library#77)

Observer test

See merge request !28

`this.connected` should stay hidden in AdapterLitElement.

(check for `this[name]` failed for value `false`)

Update all non-major dependencies

See merge request !27

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

Update dependency karma to v6

See merge request !26

TODO: translate some untranslated strings

Only subscription are supported (no single calls)

"root" provider handle all events (and cancel propagation)

(update attribute only if value changed)

Set init key/values like an other attributes: key="value"

When added in HTML a mutation observer does not recognize them...

(only a prove of concept)

Improve scroll to top behaviour

See merge request !25

Implement "set-property" handling in dbp-provider and use it in dbp-language-select (dbp/apps/library#77)

fix(deps): update all non-major dependencies

See merge request !24