send videochat-url and -invitation also through header

src/chat.rs

@@ -1636,6 +1636,7 @@ pub async fn send_videochat_invitation(context: &Context, chat_id: ChatId) -> Re
     };
 
     let mut msg = Message::new(Viewtype::VideochatInvitation);
+    msg.param.set(Param::VideochatUrl, &url);
     msg.text = Some(
         context
             .stock_string_repl_str(StockMessage::VideochatInviteMsgBody, url)