Local keybindings

It would be useful to support setting keybindings per buffer. Also it would be useful to support setting keybindings temporarily, without saving them to bindings.json.
So it seems natural to implement local keybindings, similar to local options: per buffer, without saving to bindings.json.

Any thoughts on it?

A simple use case for it: keybindings for command mode only.
A more elaborate use case: in my init.lua I implemented a simple "view mode" which makes micro behave somewhat like a less-like pager. It temporarily sets readonly=true and remaps some keys (e.g. "n" to FindNext, "q" to Quit). Currently, with global keybindings, it is quite messy. I want to enable/disable view mode per buffer, I don't want it to affect keybindings in command mode, I don't want it to write to bindings.json each time when toggling between view mode and normal mode, and so on.

Start by reviewing the existing keybinding and local-options implementations, then determine how per-buffer and temporary bindings should interact with command mode and bindings.json. Done means the proposed behavior is defined and supported for the view-mode use cases without persisting temporary changes.