Add docs about package manifests. r=bgrins
Add docs about package manifests. r=bgrins

mozilla/tofino,victorporof/tofino,mozilla/tofino,mozilla/tofino,jsantell/tofino,jsantell/tofino,jsantell/tofino,victorporof/tofino,mozilla/tofino,bgrins/tofino,bgrins/tofino,jsantell/tofino,bgrins/tofino,bgrins/tofino