home page - add some more info about docs, generally
Created by: seanmadsen
If we want to redirect civicrm.org/documentation to docs.civicrm.org eventually, we'll need some more info on the docs home page.
Michael said It does need a bit of fleshing out. Copying content from http://civicrm.org/documentation to https://github.com/civicrm/civicrm-docs/blob/master/src/AppBundle/Resources/views/Read/home.html.twig