Guidance to add some additional functionality


Hi new Phabricator user here and was hoping the community could guide me in the direction I needed to go.

For our phabricator instance that we run, I have been asked to add some additional functionality. Mainly on a Reviewer Approval or Reviwer Decline of a review to fire off a external script to perform some action. In looking at the source code, I will admit I am getting lost as to where to exactly look to begin this modification. Any tips on where to start for this would be greatly appreciated.

Thanks in advance.