Move segmenting.py to fonttools

[m4rc1e]

Since there's no python bindings for libraqm, it may be nice to move this module further up the food chain. I personally need to use it in diffenator2 and don't fancy adding the whole of fontgoggles as a dep.

Will happily do this if you're both on board

cc @anthrotype, @justvanrossum

[justvanrossum]

I have no objections, but be aware that it depends on python-bidi, which seems to be unmaintained, and segmenting.py monkeypatches it to use unicodedata2.

Perhaps it should become a new package? I'm not sure it's a good fit for fonttools. (I'm not dead-set against it, just expressing my doubt.)

[m4rc1e]

I see. Perhaps it may be best for me to just copy the module to my own repo for now and in the future write bindings for libraqm if we encounter another repo which needs this functionality.