Examine source code of Double Click Dictionary

{
  "author": "igorlogius",
  "manifest_version": 2,
  "name": "Double Click Dictionary",
  "browser_action": {
    "default_area": "navbar",
    "default_popup": "options.html"
  },
  "description": "View definitions easily as you browse the web. Double-click any word to view its definition in a small pop-up bubble.",
  "icons": {
    "512": "icon.png"
  },
  "options_ui": {
    "page": "options.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content-script.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "storage",
    "https://www.google.com/"
  ],
  "version": "2.1.2",
  "browser_specific_settings": {
    "gecko": {
      "id": "{d2203ef5-993b-4f4f-9d9b-3483b1406e18}"
    }
  }
}