This was my first plugin. Looking back on it, it was full of bad
design decisions (and I have elected to keep most of the user-facing
ones for backwards-compatability). This merge tries to uncrustify the
plugin by standardizing the documentation, removing much unecessary
code, reorganizing the internal structures, and removing references to
my own made-up terminology.
Previously, we could set a `:h libmodal-exit-supression` flag in order
to stop the modes from automatically exiting upon an <Esc> press. This
commit adds this functionality to `Prompt`s so that the same may be done
for them.