Todo: Multi-class should allow capturing match groups

[joshgoebel]

Is your request related to a specific problem you're having?

#3081

Multi-class support does not currently allow capturing match groups. This should be allowed.

The solution you'd prefer / feature you'd like to see added...

We should count the match groups, renumber them, and also renumber the keys passed to className (to account for any new "gaps" that the capture groups have introduced). We have most of the code for this in regex.js already since we have to do a lot of this for our MultiRegexMatcher.

Any alternative solutions you considered...

None.

Additional context...

None.