Examine source code of GoogleSkinner

{
  "manifest_version": 2,
  "name": "GoogleSkinner",
  "version": "1.2",
  "description": "Changes colors and backgrounds of Google",
  "permissions": [
    "storage"
  ],
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Options",
    "default_popup": "link.html"
  },
  "options_ui": {
    "page": "main.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://google.com/",
        "*://www.google.com/",
        "*://www.google.com/?*",
        "*://google.com/?*"
      ],
      "js": [
        "skin.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "gskinner@script-js.github.io"
    }
  }
}