feat: ephemeral peer channels (#5346)

Co-authored-by: link2xt <link2xt@testrun.org>
Co-authored-by: iequidoo <117991069+iequidoo@users.noreply.github.com>

src/mimeparser.rs

@@ -199,6 +199,9 @@ pub enum SystemMessage {
 
     /// Webxdc info added with `info` set in `send_webxdc_status_update()`.
     WebxdcInfoMessage = 32,
+
+    /// This message contains a users iroh node address.
+    IrohNodeAddr = 40,
 }
 
 const MIME_AC_SETUP_FILE: &str = "application/autocrypt-setup";