Add dedicated config variable to enable compatibility with vim-visual-multi

[LunarWatcher]

See mg979/vim-visual-multi#256

The current system of detecting config variables for vim-visual-multi seem to be unreliable for detecting if it's active or not. A separate config variable should help force the right load through.

Might also be worth adding a second config variable as an override just in case. I'm pretty sure it isn't inherently bad to use auto-pairs in vim-visual-multi, but it was probably added for a good reason in the first place. Particularly with balancing, I do see ways auto-pairs would result in weird outcomes, so keeping both options open is probably a good idea

[LunarWatcher]

Closing in favour of #86