Examine source code of fullscreenit

{
  "manifest_version": 2,
  "name": "fullscreen",
  "version": "1.0",
  "description": "Allows pages to be fullscreened",
  "icons": {
    "64": "icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "index.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{034f2c8f-126b-42c1-984c-2c0a9719ddec}"
    }
  }
}