Fix comments

index.php

@@ -7,7 +7,7 @@
 	*	For educational purposes only.
 	*	The Server produces an Actor who can be followed.
 	*	The Actor can send messages to followers.
-	*	Those messages can have linkable URls and hashtags.
+	*	Those messages can have linkable URls, hashtags, and mentions.
 	*	The Server saves logs about requests it receives and sends.
 	*	This code is NOT suitable for production use.
 	*	SPDX-License-Identifier: AGPL-3.0-or-later