Coalesce Borders #251
Description
Allow borders to coalesce. See the Chess example for an idea of why this is useful.
This has a horizontal separator and a vertical separator, but they don't meet up with a T-character, making them look somewhat disjoint.
By being able to inspect borders of components for their width/height and by establishing a strategy for joining them up, it would be possible to make this seamless. Or not, if focus is enabled for a bordered component, which would make it pop forward more. As a bonus, it would cause multiple bordered components to take up less space.
Consideration should be given for how to treat scroll bars.