Examine source code of KeepCode

{
  "manifest_version" : 2 ,
  "name" : "KeepCode",
  "version" : "0.4.0",
  "description" : "Prep smarter for coding interviews! KeepCode tracks your LeetCode progress so you can focus on solving.",
  "permissions" : [
    "storage" ,
    "tabs" ,
    "activeTab" ,
    "https://leetcode.com/*" 
  ],
  "background" : {
    "scripts" : [
      "background.js" ,
      "browser-polyfill.js" 
    ],
    "persistent" : false 
  },
  "browser_action" : {
    "default_popup" : "popup/popup.html",
    "default_icon" : "icons/keepcode-icon.png"
  },
  "content_scripts" : [
    {
      "matches" : [
        "https://leetcode.com/problems/*" 
      ],
      "js" : [
        "leetcodeApi.js" ,
        "content.js" ,
        "browser-polyfill.js" 
      ]
    }
  ],
  "options_ui" : {
    "page": "options/options.html" ,
    "open_in_tab": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6d6bbc5b-f106-47cd-91e1-b9056fcc29ca}"
    }
  }
}