Readme spruce

[mwcz]

fixes #22

This is not ready to merge yet, just opening it for comments!

I arranged the docs as follows:

• README.md contains the most basic info about what the project is and how to run the demos.
• CONTRIBUTING.md contains instructions on how to create new elements, test them, etc.

The contribution guide is probably what needs the most work. I think this is what it needs in order to be relatively complete:

• docs on the theming system: var naming conventions, how to theme a new element, how to adjust the theme of an existing element
• docs on using rhelements: how to pull a RHElement into your app, using ESM vs UMD, links to Homa's example apps
• docs on the rhelement base class, such as what's in elements/rhelement/README.md
• more thorough docs on how to write tests, such as how WCT works, link to chai assertions, how to get to the actual page your elements are on while debugging tests (via network tab)
• docs on where to put rhelement-wide tests (ie: elements/all/test/)
• docs explaining the difference between demo pages and storybook (I found this really hard to explain, showing I don't fully understand the line between them)
• docs on how to version bump and publish RHElements
• perhaps howto-oriented docs instead of reference docs, such as "How to add an observed attribute"
• HOW TO LGTM

Probably more, that's all I can think of for now. Docs are hard!

@kylebuch8 I know some of the above already exists in rhelements.github.io, but I'm not sure of the best way to dedupe content between this repo and that one.

[mwcz]

I'm thinking now that this branch overlaps too much with Krystal's work on the rhelements.github.io docs site. Perhaps the repo should only contain the README (what is RHElements, and quickstart), and then link off to the docs site for all other information.

[kylebuch8]

@mwcz I agree. Let's make sure that we get things linked on the official README but I think we'll have to wait for @KrystalMoore16 to be ready.

[mwcz]

I'll update this PR to include only the README changes, and we can save any contribution guide content for Krystal's site.

[kylebuch8]

Locally Grown Trouble Maker