feat: declarative keyboard shortcut overrides

[ch1bo]

Add support to declare keyboard shortcuts to be applied on activation of the home manager generation. This follows a similar approach as the places and search modifications.

Example configuration in my dotfiles: https://github.com/ch1bo/dotfiles/blob/6dd38f41cb74269fab8ceaf865292736660ea491/home-modules/browser/zen.nix#L106-L129

    keyboardShortcutsVersion = 14; # pin to detect regressions
    keyboardShortcuts = [
      {
        id = "zen-compact-mode-toggle";
        key = "s";
        modifiers.control = true;
        modifiers.alt = true;
      }
      {
        id = "zen-compact-mode-show-sidebar"; # toggle floating sideboar
        key = "f";
        modifiers.control = true;
        modifiers.alt = true;
      }
      {
        id = "key_savePage";
        key = "s";
        modifiers.control = true;
      }
      {
        id = "key_quitApplication";
        disabled = true;
      }
    ];

[luisnquin]

I couldn't have done better, thank you very much for bringing this feature to this flake.

Your dotfiles looks solid too, I'd like to share it in the README! :)