src/vs/base/common/keybindings.ts/SimpleKeybinding/isModifierKey
class SimpleKeybinding:	public isModifierKey(): boolean {
		return (
			this.keyCode === KeyCode.Unknown
			|| this.keyCode === KeyCode.Ctrl
			|| this.keyCode === KeyCode.Meta
			|| this.keyCode === KeyCode.Alt
			|| this.keyCode === KeyCode.Shift
		);
	}