Add tachyons-rn abbrevations

[stephenh]

The default tachyons-based abbreviations assume a web environment.

We should be able to develop a subset of the tachyons abbreviations that are specifically supported in React Native / Yoga.

@KoltonG is probably going to start this, but directly in our app for faster iteration, and then we can upstream it into truss once the rules are stabilized.