[feature] Catalyst support

[bennypowers]

I bet apollo elements support for GitHub's new hotness would be cool

https://github.github.io/catalyst/guide/introduction/

at the very least, probably some mixins and a decorator or two? maybe a base class?

OTOH, is there a more idiomatic way than subclassing?

[keithamus]

Thanks for drawing my attention to this @bennypowers! Catalyst is a library on top of Web Components so it can leverage the base components you already have in this repository. I don't think there is any need for Catalyst specific versions :tada:

[bennypowers]

👋 Thanks for the feedback @keithamus. It's a nice argument in support of both the web components primitives and your library that they can come together without fuss.

I sneakily released some base classes a few versions back, which just apply the mixins to vanilla HTMLElement. That being the case, and in light of your feedback, perhaps it will be enough to just document using catalyst with some examples on the docs page.

Cheers!