Display duration of recorded voice message (#1733)

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Co-authored-by: ElementBot <benoitm+elementbot@element.io>

libraries/voicerecorder/api/src/main/kotlin/io/element/android/libraries/voicerecorder/api/VoiceRecorderState.kt

@@ -39,10 +39,12 @@ sealed class VoiceRecorderState {
      * @property file The recorded file.
      * @property mimeType The mime type of the file.
      * @property waveform The waveform of the recording.
+     * @property duration The total time spent recording.
      */
     data class Finished(
         val file: File,
         val mimeType: String,
         val waveform: List<Float>,
+        val duration: Duration,
     ) : VoiceRecorderState()
 }