FR: Allow "equivalent domains" for isolation

[Gitoffthelawn]

For a few domains, users will likely want to open them in the same container as another domain. Examples are github.com and github.community.

(Of course, GitHub should have really just used community.github.com, but they chose not to.)

Would it be possible to add a feature to TC so the user can indicate, for the purposes of isolation, those domains are equivalent?

[stoically]

This would probably also be possible with the approach outlined in #397, where you could have multiple target domains belonging to one rule. Not sure if I will ever get around doing it myself, but I'd love to see that functionality in a container add-on.