send out videochat-invitation message, set up fallback text

src/stock.rs

@@ -210,6 +210,12 @@ pub enum StockMessage {
 
     #[strum(props(fallback = "Message deletion timer is set to 4 weeks."))]
     MsgEphemeralTimerFourWeeks = 81,
+
+    #[strum(props(fallback = "Videochat invitation"))]
+    VideochatInvitation = 82,
+
+    #[strum(props(fallback = "You are invited to an videochat, click %1$s to join."))]
+    VideochatInviteMsgBody = 83,
 }
 
 /*