[meta] Creating an author-focused entry point summarizing the state of CSS

As requested by folks on the call, I'm starting a new issue to explore the tangent I started in #4715 (which is about publishing a new Snapshot) — can we make such a thing that is more useful for authors?

Specific aspects of a summary publication that have been brought up:

• a single-source quick guide to CSS properties (etc.) that's more than an index where you need to click through for any details

• information about both spec stability and implementation status, again as a quick guide for authors

• obvious milestones / names to refer to new CSS & get people excited about the features that are now available

This doesn't need to happen in the Snapshot note. It doesn't even need to happen in a traditional W3C Technical Report format. When I mentioned the snapshots on CSS-Tricks as the closest thing the working group has to an overarching “CSS4”, Chris Coyier's response was:

If it were me, I’d hire a content strategist and a designer, and get them going on a microsite or landing page that delivers with crystal clarity what “CSS2019” is. I could get behind that. The snapshot landing page as-is is too dry.

Maybe it would be better to start from something like the working group website's “current work” page, which is also a great resource/overview that isn't well known. Or work with MDN folks to build something on their platform.

Start with issue #4715 and the existing Snapshot publication, then review the CSS Working Group's “current work” page and the proposed MDN collaboration. Compare the possible author-facing formats and define what a completed overview must provide for CSS properties, specification stability, implementation status, and feature milestones.