Explain how to watch MRs in specific folders

I forgot where to add people as path watchers for athena, and it took digging into email to find the right location (https://gitlab.cern.ch/atlas-sit/CI/-/blob/master/data/watch_list.py, https://gitlab.cern.ch/atlas-sit/CI/-/blob/master/data/domain_map.py?ref_type=heads). It'd be helpful to have this listed, maybe under Tips & Tricks in the Gitlab Workflow section.

Self-assigned but I'd wait a bit in case there's any other opinion on this and/or where it should go.