Examine source code of Codeforces Theme Changer

{
  "manifest_version": 2,
  "name": "Codeforces Theme Changer",
  "version": "1.0",
  "description": "Change the theme of Codeforces",
  "permissions": [
    "activeTab",
    "storage"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "images/icon16.png",
      "48": "images/icon48.png",
      "128": "images/icon128.png"
    }
  },
  "web_accessible_resources": [
    "themes/*.css"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "*://codeforces.com/*"
      ],
      "css": [
        "themes/default.css"
      ],
      "js": [
        "scripts/content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{a215c35a-64a7-4983-9937-eabac94c0341}"
    }
  }
}