Examine source code of Wikiclick

{
  "manifest_version": 2,
  "name": "Wikiclick",
  "version": "1.2",
  "description": "Displays a popup wikipedia summary when you highlight a term.",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "wikiclick.js"
      ]
    }
  ],
  "permissions": [
    "<all_urls>"
  ],
  "browser_action": {
    "default_icon": "icons/wiki.png",
    "default_title": "Wikiclick",
    "default_popup": "popup/popup.html"
  }
}