Currently Buffer::set_rich_text uses a lot of allocations, even when reconstructing a buffer. Ideally most or all of these allocations could be amortized using cached buffers and reusing allocations within the Buffer more aggressively. A full solution would require passing buffers and buffer sources to the method, so maybe a new method could be added for use-cases where full optimization is important (e.g. bevy).

As an aside, the Family::Name variant contains a String but it would make more sense as a SmolStr.