This commit adds a standalone state type for manipulating
and displaying text. It reads text from a minimal interface,
shapes it, tracks valid cursor positions, and provides sizing
and scrolling services to higher-level widgets. My long term
goal with these types is to export them to allow non-core widgets
to build atop them, but I've left them private for now.
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
Chris Waldon