add message var to chat message deleted trigger (#386)

Author: FajitaOfTreason

streamerbot/3.api/2.triggers/twitch/moderation/chat-message-deleted.md

@@ -7,7 +7,10 @@ variables:
   - name: targetMessageId
     type: string
     description: The unique identifier for the message that has been deleted
+  - name: message
+    type: string
+    description: Text content of the deleted message
 commonVariables:
   - TwitchBroadcaster
   - TwitchUser
----
+---