* Added `in_thread` parameter to `evt.reply()` and `evt.respond()`.
* By default, responses will go to the thread if the command is in a thread.
* By setting the flag to `True` or `False`, the plugin can force the response
to either be or not be in a thread.
* Fixed static files like the frontend app manifest not being served correctly.
* Fixed `self.loader.meta` not being available to plugins in standalone mode.
* Updated to mautrix-python v0.19.6.