Adding a note to the package review guidelines

[Nigel Jones]

I think it'd be a good idea to make a note on the Package Review
Guidelines/checklist effectively saying:

"Potential reviewers are encouraged to please check that the
reportee/submitter of a review request is current in the cvsextras package
group before commencing a review"

There is a dynamically generated list that I generally work off from
admin.fp.o, but I'm sure there is the potential to create a static list
(or provide another means to check if a contributor is able to commit
their packages to CVS (of course, this wouldn't apply to people that could
sponsor someone).

I know this would normally go to the fedora-packaging list, but I think
this is more of a reminder than policy that should be added.