kakounePlugins: Add 5 kakoune plugins (#67593)

* kakounePlugins: Add 5 kakoune plugins

Should be compatible with
https://github.com/NixOS/nixpkgs/pull/64310

* kak-auto-pairs: for automatic closing of pairs
* kak-buffers: for easier buffer management
* kak-fzf: for fzf integration
* kak-powerline: for a prettier modeline
* kak-vertical-selection: for easy vertical selections

* kakounePlugins: alphabetize package list

* kakounePlugins.kak-fzf: add ability to choose between fzf/skim

* kakounePlugins.kak-powerline: substitute full path to git binary