Update iframe-events.md

docs/dev-guide/iframe-events.md

@@ -726,6 +726,7 @@ The listener receives an object with the following structure:
     on: boolean // new recording status - boolean,
     mode: string // recording mode, `local`, `stream` or `file`,
     error: string | undefined // error type if recording fails, undefined otherwise
+    transcription: boolean // whether a transcription is active or not
 }
 ```