feat(config): Add useHostPageLocalStorage

config.js

     // Sets the conference subject
     // subject: 'Conference Subject',
 
+    // This property is related to the use case when jitsi-meet is used via the IFrame API. When the property is true
+    // jitsi-meet will use the local storage of the host page instead of its own. This option is useful if the browser
+    // is not persisting the local storage inside the iframe.
+    // useHostPageLocalStorage: true,
+
     // List of undocumented settings used in jitsi-meet
     /**
      _immediateReloadThreshold

react/features/base/config/configWhitelist.js

     'stereo',
     'subject',
     'testing',
+    'useHostPageLocalStorage',
     'useTurnUdp',
     'videoQuality.persist',
     'webrtcIceTcpDisable',

react/features/base/jitsi-local-storage/setup.web.js

 import logger from './logger';
 
 declare var APP: Object;
+declare var config: Object;
 
 /**
  * Handles changes of the fake local storage.
     APP.API.notifyLocalStorageChanged(jitsiLocalStorage.serialize());
 }
 
+/**
+ * Checks if the local storage of the host page needs to be used instead jitsi-meet's local storage.
+ *
+ * @param {Object} urlParams - Object with parsed URL params.
+ * @returns {boolean} - True if the local storage of the host page needs to be used instead jitsi-meet's local storage
+ * and false otherwise.
+ */
+function shouldUseHostPageLocalStorage(urlParams) {
+    // NOTE: normally the url params and the config will be merged into the redux store. But we want to setup the local
+    // storage as soon as possible, the store is not created yet and the merging of the URL params and the config
+    // haven't been executed yet. That's why we need to manually parse the URL params and also access the config trough
+    // the global variable.
+    if (urlParams['config.useHostPageLocalStorage'] === true
+        || (typeof config === 'object' && config.useHostPageLocalStorage)) {
+        return true;
+    }
+
+    if (jitsiLocalStorage.isLocalStorageDisabled()) { // We have detected that ou own local storage is not working.
+        return true;
+    }
+
+    if (browser.isWebKitBased()) { // Webkit browsers don't persist local storage for third-party iframes.
+        return true;
+    }
+
+    return false;
+}
+
 /**
  * Performs initial setup of the jitsiLocalStorage.
  *
  * @returns {void}
  */
 function setupJitsiLocalStorage() {
-    if (jitsiLocalStorage.isLocalStorageDisabled() || browser.isWebKitBased()) {
-        const urlParams = parseURLParams(window.location);
+    const urlParams = parseURLParams(window.location);
 
+    if (shouldUseHostPageLocalStorage(urlParams)) {
         try {
             const localStorageContent = JSON.parse(urlParams['appData.localStorageContent']);