send videochat-url and -invitation also through header

src/param.rs

@@ -68,6 +68,9 @@ pub enum Param {
     /// For Messages
     AttachGroupImage = b'A',
 
+    /// For Messages
+    VideochatUrl = b'V',
+
     /// For Messages: space-separated list of messaged IDs of forwarded copies.
     ///
     /// This is used when a [crate::message::Message] is in the