Support User Extensions #9
Description
Beyond the most basic functionality, features should be added via extensions.
This needs an interface for loading in extensions and their config via url.
Some extensions can be kept in the same repo and served from the same domain for perf, other extensions can be loaded from 3rd parties and kept in the service worker and updated in the normal webby way when network is available.
Perhaps 3rd party extensions could be downloaded and stored locally but this makes managing update state more awkward.