Examine source code of Intulse Click to Call

{
  "name": "Intulse Click to Call",
  "description": "Click to dial/call directly from your helpdesk, CRM, sales software or any web site",
  "version": "1",
  "permissions": [
    "tabs",
    "http://*/*",
    "https://*/*"
  ],
  "browser_action": {
    "default_title": "Intulse click to dial",
    "default_icon": "images/appicon_16x16.png",
    "default_popup": "popup.html"
  },
  "icons": {
    "16": "images/appicon_16x16.png",
    "48": "images/appicon_48x48.png",
    "128": "images/appicon_128x128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "css": [
        "css/content.css"
      ],
      "js": [
        "js/jquery.js",
        "js/content.js"
      ]
    }
  ],
  "background": {
    "persistent": true,
    "scripts": [
      "js/jquery.js",
      "js/background.js"
    ]
  },
  "manifest_version": 2
}