[REQUEST] `expand_unprintable` option

### Feature Apologize if I'm in the wrong place. please add an `expand_unprintable` option that makes the function [`expand_unprintable()`](https://github.com/mawww/kakoune/blob/df7b33bc7b9da897d1d0127b54ae1e629d2334ff/src/highlighters.cc#L1279-L1309) behave normally when it's true, otherwise disables the *expansion* of unprintable characters. this can be acheived by modifying the condition inside the `expand_unprintable()` function (in the `highlighters.cc` file on line 1294) ### Usecase Rather than displaying in a terminal directly and losing kakoune keybinds/plugins, give the users the option. Makes kakoune a better pager (of course it's easier than making a separate kakpager program or asking the user to use an alternative pager). Please.