[report] Add text about declarative custom elements as lower-level spec use-case

[justinfagnani]

Declarative custom elements should be sketched out as a way to verify that other specs that it depends on are suitable to use for it. This includes things like template instantiation's built-in syntax, declarative CSS modules, various element internals APIs, etc.

[thescientist13]

So for the 2022 report we were able to get this in via #41, so if there is anything missing from this issue that isn't covered in that draft, then I think it would be good to switch the tag for this one TPAC 2022, otherwise maybe this one can be closed?

cc: @EisenbergEffect

[EisenbergEffect]

Not sure if we should close this. We might want to rename/repurpose it. Mainly, the current report is just reporting on the current status. No attempt to fix things. I think we need to do separate work to basically create an updated proposal that aligns with all the other specs since things have evolved quite a bit since the original declarative custom elements proposal was written. The report does outline a number of related specs and open questions that can help direct that effort though.

[thescientist13]

got it, yeah that might be good context to add in terms of status / next steps. Will tag this with our label for the 2022 report so it can stay on our radar.