Web Audio: Call the onStop callback when the device is stopped.

mini_al.h

@@ -19082,6 +19082,11 @@ mal_result mal_device__stop_backend__webaudio(mal_device* pDevice)
         mal.get_device_by_index($0).webaudio.suspend();
     }, pDevice->webaudio.index);
 
+    mal_stop_proc onStop = pDevice->onStop;
+    if (onStop) {
+        onStop(pDevice);
+    }
+
     return MAL_SUCCESS;
 }