add channel ID, expand readme

config.py

@@ -6,4 +6,4 @@ WEBSOCKET_INITIAL_BACKOFF = 5.0
 CLIP_DIRECTORY, TEMP_DIRECTORY, CLIP_QUANTITY = None, None, None
 PEERTUBE_HOST, PEERTUBE_USER, PEERTUBE_PASS = None, None, None
 OWNCAST_HOST, OWNCAST_AUTH = None, None
-AUTHENTICATION_REQUIRED, PT_API_BASE = None, None
+AUTHENTICATION_REQUIRED, PT_API_BASE, PEERTUBE_CHANNEL_ID = None, None, None