Examine source code of Quick Focus

{
  "manifest_version": 2,
  "name": "Quick Focus",
  "version": "1.0",
  "author": "jljse",
  "homepage_url": "https://github.com/jljse/addon-quickfocus",
  "description": "Provide keyboard tab navigation to quickly move focus to the elements on screen.",
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{2a427ef9-4db1-4daf-8264-f3c3e6d062d8}"
    }
  },
  "icons": {
    "48": "icons/quickfocus-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "src/defaultOptions.js",
        "src/quickfocus.js"
      ]
    }
  ],
  "options_ui": {
    "page": "src/options.html",
    "browser_style": true
  }
}