v21.0.0
doc/start: add vstart install guide
doc/start/ceph.conf: trim the sample ceph.conf file
doc/start: Fix stray RST syntax in documenting-ceph.rst
doc/start: Update and fix get-involved.rst
doc/start: Add ARM support note to hardware-recommendations.rst
doc/start: Mention RGW in Intro to Ceph
doc: Fix minor formatting, typo etc issues
doc: Improve start/quick-rbd.rst