Document and socialize ddev-ui structure, technologies

[rfay]

What happened (or feature request):

We need to have a broader understanding of ddev-ui's code and structure and technologies.

The goal would be to have basic architecture docs that could live on, either in the repo (best case, maybe in a devdocs directory?), or in a linked gdoc or some such.

And we need to try to get more people understanding this, so will meet Nov 1 to start that process.