Improve README with even more crisp FAQ answers to existential questions

@rsheeter and I were chatting about these examples again today, and as a next step, I'd like to nail down

1. why we need to ship code inside fonts
2. why other options (state machine? new layout tables or algorithms?) aren't sufficient, and
3. why doing this is valuable enough to justify requiring a full blown runtime to render text

This repo already has some promising starting points, but more can be said in order to inspire adoption – very clear answers to, what are the things that everyone should agree are worth caring about, and how this does make those things better in ways that have no viable alternatives.