Make sure that only text messages can be edited

src/qml/MessageDelegate.qml

@@ -146,6 +146,11 @@ TimelineDelegate {
      */
     required property bool isPending
 
+    /**
+     * @brief Whether the event can be edited by the local user.
+     */
+    required property bool isEditable
+
     /**
      * @brief Whether an encrypted message is sent in a verified session.
      */