update the "join the multimedia team" page

[IOhannes m zmölnig (Debian/GNU) <umlaeute@debian.org>]

hi,

i've just updated the join-the-team page to direct people to salsa.d.o
instead of alioth.

i wonder however, what the current guidelines are rearding the mailinglists.

i guess, new users should be advised to just join
debian-multimedia@l.d.o (and all mentions of pkg-multimedia@a.d.o should
be removed completely; even though that list has been migrated.)

also the references to pkg-multimedia-commits@a.d.o should be dropped
completely.

is this correct?

fgasdmr
IOhannes