Support listing multiple files/folders for a single "mention" configuration

[RalfJung]

Sometimes one wants to group together a bunch of files/folders and have them all watched by a team. A particularly common pattern for this is folder/name.rs+folder/name/. It would be nice if triagebot support somehow configuring this in one go, instead of having to repeat the configuration for both patterns. Maybe it could even support folder/name*, or some special syntax to specifically cover both name.rs and name/ (since that's how Rust modules work)?

[tgross35]

I would much prefer this matcher use globs instead of starts_with. That would work here, in addition to making it easy to find something like **/unix that exists in more varied locations.