Examine source code of Dictionary Pop

{
  "manifest_version": 2,
  "name": "Dictionary Pop",
  "version": "1.0",
  "description": "Double-click on a word to display its definition from various dictionaries instantly.",
  "permissions": [
    "activeTab",
    "http://*/",
    "https://*/"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{b606fd5f-0782-421b-980d-c41e5b73dacc}"
    }
  }
}