Improve the introduction page

[jamesmunro]

Intro page enhancements https://docs.arcticdb.io/

• it only shows how to install with pip
• 'LMDB' is not obvious
• Why highlight just VAST storage? - lets have a table of storage backend support, maybe on another page
• Using aws sdk auth is better practice than accesskey in URI
• Lots of detail on how to connect to s3, not enough on azure, lmdb is a snippet mentioned differently. Display all these options consistently and minimally on the frontend, use a sub page for detail.
• The rest of the page is a decent intro to the basics.

Related: https://github.com/man-group/ArcticDB/issues/777