Add notes to the README file [ci skip]
Add notes to the README file [ci skip]

Mention that a renderer should implement at the very least a `paragraph`
method (e.g. when inheriting from Redcarpet::Render::Base). Also update
the autolink option description to document the parsing of anchors.

vmg/redcarpet,emq/redcarpet,increments/greenmat,kattybilly/redcarpet,emq/redcarpet,liquorburn/redcarpet,Hacker0x01/redcarpet,gitcafe-dev/redcarpet,increments/greenmat,liquorburn/redcarpet,increments/greenmat,kattybilly/redcarpet,liquorburn/redcarpet,vmg/redcarpet,kaneshin/redcarpet,kattybilly/redcarpet,kaneshin/redcarpet,vmg/redcarpet,kaneshin/redcarpet,kattybilly/redcarpet,be9/redcarpet,Hacker0x01/redcarpet,gitcafe-dev/redcarpet,fukayatsu/redcarpet,vmg/redcarpet,Hacker0x01/redcarpet,emq/redcarpet,liquorburn/redcarpet,gitcafe-dev/redcarpet,Hacker0x01/redcarpet,kaneshin/redcarpet,fukayatsu/redcarpet,be9/redcarpet,fukayatsu/redcarpet,emq/redcarpet,be9/redcarpet,be9/redcarpet,increments/greenmat,fukayatsu/redcarpet