2021-01-12: text rendering with an eye to non-English

Beginnings of a text-rendering system for the Mu computer, which is built up from machine code and intended to be taken apart. Even though there's much about Mu that's bare-bones and minimalist, I care very much about supporting people who want to customize it to their own language, even if it's written right-to-left or some other, more esoteric way. Main project page: https://github.com/akkartik/mu