Add badge for converting to Btrfs
The badge title and description were written by Matthew Miller,
and the artwork is courtesy of Máirín Duffy.
This badge is intended to be manually awarded, but having a rules
file makes it much easier to populate it rather than doing so by hand...
Co-authored-by: Matthew Miller <mattdm@mattdm.org>
Co-authored-by: Máirín Duffy <fedora@linuxgrrl.com>