Add documentation about reviewing pull requests on language tracks
Add documentation about reviewing pull requests on language tracks

This should help both contributors and maintainers provide a comprehensive review when pull requests are
submitted to the individual language track repositories.

In particular, this focuses quite strongly on how to review a pull request that adds or changes an exercise.

mhelmetag/exercism.io,tejasbubane/exercism.io,tejasbubane/exercism.io,nathanbwright/exercism.io,RaptorRCX/exercism.io,RaptorRCX/exercism.io,jtigger/exercism.io,nathanbwright/exercism.io,treiff/exercism.io,RaptorRCX/exercism.io,treiff/exercism.io,mhelmetag/exercism.io,nathanbwright/exercism.io,jtigger/exercism.io,treiff/exercism.io,tejasbubane/exercism.io,jtigger/exercism.io,treiff/exercism.io,nathanbwright/exercism.io,RaptorRCX/exercism.io,tejasbubane/exercism.io,mhelmetag/exercism.io,jtigger/exercism.io,mhelmetag/exercism.io