Add join_room

mytrix.py

@@ -80,6 +80,12 @@ class Matrix:
 
         return self._put(endpoint, json_data=content)
 
+    def join_room(self, room):
+        """Join a room using its ID."""
+        endpoint = "/r0/rooms/%s/join" % (room,)
+
+        return self._post(endpoint)
+
     def send_room_message(self, room, text, msgtype="m.text"):
         """Send a message event to a room."""
         content = {"msgtype": "m.text", "body": text}