Replace current `home.md` and `home.html` with simpler document

I don't like this page depending on a VSCode plugin to recreate... 
Instead, link directly to a markdown file on Github and let Github handle rendering to html

- [ ] Create simple markdown doc
    - [ ] Brief intro
    - [ ] How to use
    - [ ] What it is like for participants
- [ ] On home tab, link directly to Github page for that doc
- [ ] Erase current `home.html`