Feature: Switchable Backends

[nrdxp]

This is definitely a request for the far future, but it may be good to brainstorm early.

I see onivim shaping up to be quite possibly an ideal editor in a lot of ways, but for me, there is something I would really desire to have in an editor like this. Currently I am a heavy user of kakoune, and have been keeping a close eye on helix as well, which is a bit inspired from it.

It would be incredible if Oni could one day allow for switchable backends, so that instead of loading libvim, one could load an alternative editor like those mentioned above. Helix may be particularly suited for this as it is designed from the ground up to be quite modular so that it can be incoorperated into a graphical editor. I'm sure even EMACS users would love to see a backend someday, but that may be a bit too divergent (but maybe not).

I'm not sure how tightly coupled libvim is to the UI, but it'd be awesome to see this as a feature someday.