Text rendering documentation

[janpaul123]

• Under Rendering -> API Overview we should add "Text" and talk about how it works
• We should also add some tips for crisp rendering, including using something like the Digital Color Meter on Mac to look at it
• Also let's link to the tickets of things that we still have to do, like Text rendering "megathread" #169 Text rendering debugger #174 Crisp text rendering when positions are integer values #175