Add new encryption scheme in chrome addon/firefox webextension

chrome_addon/compat.js

@@ -19,6 +19,7 @@
 
 function getPref(key)
 {
+    // Inspired from https://github.com/akiomik/chrome-storage-promise/
     var promise = new Promise((resolve, reject) => {
         chrome.storage.local.get(key, (items) => {
             let err = chrome.runtime.lastError;