Properly release audio focus when done with call

@@ -3,6 +3,7 @@ package io.livekit.android.sample
 import android.media.AudioManager
 import android.os.Bundle
 import android.os.Parcelable
+import android.os.PersistableBundle
 import androidx.appcompat.app.AppCompatActivity
 import com.github.ajalt.timberkt.Timber
 import com.google.android.material.tabs.TabLayoutMediator
@@ -80,6 +81,13 @@ class CallActivity : AppCompatActivity() {
         }
     }
 
+    override fun onDestroy() {
+        super.onDestroy()
+
+        val audioManager = getSystemService(AUDIO_SERVICE) as AudioManager
+        audioManager.abandonAudioFocus(null)
+    }
+
     companion object {
         const val KEY_ARGS = "args"
     }