group: toggle show/hide with signal number (for keybinding)

[coreydoughty]

Adds the use of a signal number to toggle show/hide of a group module. Used in keybindings or similar.

Example config.jsonc:

{
  // ...
  "group/mygroup": {
    "signal": 1,
    "modules": [
      "...",
      "..."
    ],
    "drawer": {
      "children-class": "hidden",
      "click-to-reveal": true
    }
  },
  // ...
}

Example usage to show/hide:

pkill -RTMIN+1 waybar &

[Invertisment]

I implemented this to hide/show whole waybar: #3928

It's not yet merged for about two months but I'm using it without issues and it could probably be extended for your usecase.
i.e. to do internal broadcast of "hide group + show group"

This is my fork: https://github.com/Invertisment/Waybar