wc-apreggio

This is a proof of concept implementation for an extension for the [way-cooler compositor](https://github.com/way-cooler/way-cooler).
This extension enables easy addition of modal key-bindings inspired by Vi.
Instead of carrying out an action after hitting a key-combination, a mode may be entered instead where new key-combinations are made available.
You could set `Alt+m` to enter `move`-mode for instance, where the arrow keys can be used to move the current window until you press `return` or `escape`.
`escape` exits to `normal`-mode by default. When starting to enter keys of chain-bindings, `escape` resets the state to the beginning of the current mode, i.e. in the example below after pressing `Alt+s` to enter `spawn`-mode and then pressing `f` followed by `escape` returns to `spawn`-mode proper. A second `escape` would return to `normal`-mode.

It basically works, but needs proper documentation, testing and should probably come with more complete sample bindings.
The project is currently in hibernation, as the machine I am planning to run Way-Cooler on is rather weak and the compositor runs quite slow compared to Awesome, my current WM of choice.
I am hoping the planned port to [wlroots](https://github.com/swaywm/wlroots-rs) will improve this.

To use this extension, add the following to your `init.lua`:
```
--load apreggio
local apreggio = require("apreggio")

--create some shortcuts and convenience functions
local Mode = apreggio.Mode
local key = apreggio.key
local chain = apreggio.chain
local spawn_once = util.program.spawn_once
--return back to normal mode after spawning a program
local function spawn_return(prg)
  return function()
    util.program.spawn(prg)
    normal:mode()()
  end
end

--add some modes
local normal = Mode.new()
local spawn = Mode.new("spawn")
local move = Mode.new("move")

--add respective key bindings
normal:add({
  key({ mod }, "s", spawn:mode()),
  key({ mod }, "return", spawn_once("termite")),
  key({ mod }, "m", move:mode()),
})

spawn:add({
  key("s", spawn_return("termite")),
  chain({ "f", "x" }, spawn_return("firefox")),
  chain(
    {
      { { "shift" }, "f", },
      "x"
    },
    spawn_return("firefox")
  ),
})

move:add({
  key("left", "move_active_left"),
  key("down", "move_active_down"),
  key("up", "move_active_up"),
  key("right", "move_active_right"),
  key("return", normal:mode()),
})

normal:enter()
```