Support use of updated custom-elements.json file

[brion-fuller]

Is your feature request related to a problem? Please describe
custom-elements.json has changed over the years and currently not integrated with autogenerating of args for web components. Add support for https://github.com/webcomponents/custom-elements-manifest

Describe the solution you'd like
I would like to map the new schema in support for auto generated args.

Are you able to assist to bring the feature to reality?
Yes

[shilman]

That sounds great. Will the processing be backwards compatible? That's my only concern if we're trying to get this out in 6.3.

[brion-fuller]

Yeah I think it should be. I was planning to add a mapper for different versions because it’s still not a stable spec.

[Niznikr]

Could we also add support for the current spec for @storybook/lit so we can use something like setCustomElements that @storybook/web-components uses? Would love to start using @storybook/lit but it currently does not generate an API table for components.