message: Introduce `COMMAND` constant to `keyboard::Modifiers`
diff: @@ -28,6 +28,18 @@ bitflags! {
  }
  impl Modifiers {
  + /// The "command" key.
  + ///
  + /// This is normally the main modifier to be used for hotkeys.
  + ///
  + /// On macOS, this is equivalent to `Self::LOGO`.
  + /// Ohterwise, this is equivalent to `Self::CTRL`.
  + pub const COMMAND: Self = if cfg!(target_os = "macos") {
  + Self::LOGO
  + } else {
  + Self::CTRL
  + };
  +
  /// Returns true if the [`SHIFT`] key is pressed in the [`Modifiers`].
  pub fn shift(self) -> bool {
  self.contains(Self::SHIFT)
  