set-face now takes a scope argument, and faces can be overridden on
a buffer or window basis.
colorscheme apply on global scope, which should be good enough for
now.
Fixes#1411
When on an end of line, certain behaviours can be surprising, for
example delete will join the following line (which makes sense, and
is consistent, but hard to predict if we do not know the cursor is
on and end of line).
As Kakoune is moving more and more towards treating end of lines
as any other character, making it clear when the cursor lies on
them seems like a good way to reduce surprise.
