Track BetterTouchTool settings

[0xdevalias]

Settings/presets can be exported as a *.bttpreset file, which is a json file.

Double check it doesn't contain anything sensitive, then track it here + add helpers to more easily import/export (from CLI/setup script?)

Can we also change the default directory where the raw settings/profile is saved to somewhere tracked within this repo (or symlink it?)

It might also make sense to be able to dump/track this as part of our brew-lists command?