fix(notifications) Add timeout for video/audio lost notifs

react/features/base/devices/middleware.js

     }
 };
 
+const WARNING_DISPLAY_TIMER = 4000;
 
 /**
  * A listener for device permissions changed reported from lib-jitsi-meet.
             description: additionalCameraErrorMsg,
             descriptionKey: cameraErrorMsg,
             titleKey
-        }));
+        }, WARNING_DISPLAY_TIMER));
 
         if (isPrejoinPageVisible(store.getState())) {
             store.dispatch(setDeviceStatusWarning(titleKey));
             description: additionalMicErrorMsg,
             descriptionKey: micErrorMsg,
             titleKey
-        }));
+        }, WARNING_DISPLAY_TIMER));
 
         if (isPrejoinPageVisible(store.getState())) {
             store.dispatch(setDeviceStatusWarning(titleKey));

react/features/notifications/actions.js

  * Queues a warning notification for display.
  *
  * @param {Object} props - The props needed to show the notification component.
+ * @param {number} timeout - How long the notification should display before
+ * automatically being hidden.
  * @returns {Object}
  */
-export function showWarningNotification(props: Object) {
+export function showWarningNotification(props: Object, timeout: ?number) {
     return showNotification({
         ...props,
         appearance: NOTIFICATION_TYPE.WARNING
-    });
+    }, timeout);
 }
 
 /**