show the current recording duration at the bottom

app/src/main/kotlin/com/simplemobiletools/voicerecorder/activities/MainActivity.kt

@@ -89,6 +89,7 @@ class MainActivity : SimpleActivity() {
     }
 
     private fun initVoiceRecorder() {
+        updateRecordingDuration(0)
         toggle_recording_button.setOnClickListener {
             toggleRecording()
         }
@@ -105,6 +106,10 @@ class MainActivity : SimpleActivity() {
         }
     }
 
+    private fun updateRecordingDuration(seconds: Int) {
+        recording_duration.text = seconds.getFormattedDuration()
+    }
+
     // mp4 output format with aac encoding should produce good enough mp3 files according to https://stackoverflow.com/a/33054794/1967672
     private fun startRecording() {
         val baseFolder = if (isQPlus()) {