Document installation limitaitons, OS recommendations and options for RPM plugin
CLOSED - CURRENTRELEASE
Since Pulp RPM plugin has multiple dependencies (libmodulemd, zchunk, libsolv, etc) provided by Fedora/Centos/RHEL only (and also not by every version of those OS provides everything what we need), we need to document what the options for those who wants to use Pulp RPM plugin are.
Specify installation methods of rpm plugin
Add 'Requirements' to the docs as rpm plugin can be installed only on specific distributions.
closes #5228 https://pulp.plan.io/issues/5228