docs(readme): add quickstart + web script

[valgaze]

Please read and mark the following check list before creating a pull request:

• [x] I read and followed the CONTRIBUTING.md guide.

Short description of what this resolves:

Make 1st-time developer experience of this repo friendlier

• [ ] Add quick-start steps in main readme, also try to call-out DEV_DOCS per this issue

• [ ] Add "web" start script for above in root package.json