doc(testing/actions): fill missing in 'setConnectionState'

react/features/testing/actions.js

 
 import { SET_CONNECTION_STATE } from './actionTypes';
 
+// eslint-disable-next-line jsdoc/require-description-complete-sentence
 /**
  * Sets the conference connection state of the testing feature.
  *
  * @param {string} connectionState - This is the lib-jitsi-meet event name. Can
- * be on of:
+ * be one of (with the string values at the time of this writing):
+ * <li>{@link JitsiConferenceEvents.CONNECTION_ESTABLISHED}
+ * - ("conference.connectionEstablished"</li>
+ * <li>{@link JitsiConferenceEvents.CONNECTION_INTERRUPTED}
+ * - ("conference.connectionInterrupted")</li>
+ * <li>{@link JitsiConferenceEvents.CONNECTION_RESTORED}
+ * - ("conference.connectionRestored")</li>
+ * In the reducer the value will be an empty string until first event is
+ * received.
+ *
  * @returns {{
  *     type: SET_CONNECTION_STATE,
  *     connectionState: string