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}"
    }
  }
}