[Feature request] Tooltip support

[ImFstAsFckBoi]

Adding the ability to draw tooltips at the cursor for autocompletes, LSP documentation, etc. is really the only feature that I miss in micro compared to Emacs, Neovim, etc.

Its implementation should not be too disruptive to the codebase either, only an optional API that can be adopted picewise by plugins.

Has anyone worked on this previously? I've whipped up a small test implementation and modified the LSP hover command to use it here: https://github.com/ImFstAsFckBoi/micro/tree/feat/tooltip. If anyone already has a better implementation, then maybe that one should be used instead, but if no one want to work on it, I would be happy to do it.