Consider new docs indexing

[Ed McDonagh]

I like the way Read the Docs have the index for their docs, with titles sections with icons, and the index not repeated on the home page.

See

• https://docs.readthedocs.io/ for the result, and
• github (latest at the time of creating this issue) for the code

I’m not sure what we’d put on the index page instead, but I’m sure we can put something more interesting and inviting than a list of pages.

‌