suggestion: add advanced example with threading to docs

[recallmenot]

Hi, I've been trying to use sshkeyboard for the GUI in a websockets-based client application. The main application is running in the main asyncio loop and I ended up running sshkeyboard in a separate thread. I also wanted to have a way to stop sshkeyboard from the main thread, instead of just with an until-key. I'd like to propose adding something akin to the following to the docs so people won't spend so much time beating their head against a wall:

    async def sshkeyboard_listener(self):
        await sshkeyboard.listen_keyboard_manual(
            on_press=self.key_handler
        )

    async def sshkeyboard_monitor_stop(self):
        while self.sshkeyboard_stop is not True:
            await asyncio.sleep(0.101)

        sshkeyboard.stop_listening()

    async def sshkeyboard_coroutine_launcher(self):
        await asyncio.gather(
            self.sshkeyboard_listener(),
            self.sshkeyboard_monitor_stop()
        )

    def sshkeyboard_loop(self):
        asyncio.run(self.sshkeyboard_coroutine_launcher())

    def sshkeyboard_start(self):
        self.sshkeyboard_thread = threading.Thread(
            target=self.sshkeyboard_loop,
            daemon=True
        )
        self.sshkeyboard_thread.start()
        print("sshkeyboard thread started.")

    def sshkeyboard_shutdown(self):
        self.sshkeyboard_stop = True

        if self.sshkeyboard_thread and self.sshkeyboard_thread.is_alive():
            self.sshkeyboard_thread.join()

        self.sshkeyboard_thread = None

        print("sshkeyboard thread shut down")

    def key_handler(self, key):
        if key == 'q':
            print("'q' pressed, shutting down")
            self.exit_reason = ExitStates.Shutdown
            asyncio.run_coroutine_threadsafe(
                self.terminate(), self.asyncio_loop)

Having keyboard input in applications running other stuff with asyncio could be much easier with such an example. Anyways, thank you very much for the amazing library!