Examine source code of Google Explorer

{
  "manifest_version": 2,
  "name": "Google Explorer",
  "version": "1.0.1",
  "description": "Collect word in google.com search page",
  "icons": {
    "48": "img/icon-48.png"
  },
  "background": {
    "scripts": [
      "js/background.js"
    ]
  },
  "browser_action": {
    "default_icon": "img/icon.png",
    "default_title": "Google Explorer",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.google.com/*"
      ],
      "js": [
        "js/jquery-3.3.1.min.js",
        "js/content-script.js"
      ],
      "css": [
        "css/custom.css"
      ],
      "run_at": "document_start"
    }
  ],
  "permissions": [
    "notifications",
    "webRequest",
    "webRequestBlocking",
    "storage",
    "http://*.google.com/*",
    "https://*.google.com/*",
    "tabs",
    "activeTab"
  ],
  "homepage_url": "https://addons.mozilla.org/en-US/developers/addon/google_search_explorer"
}