Document the project's policy regarding publishing and maintaining
official OpenZFS releases.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#11821
Brian Behlendorf