Examine source code of Asterisk Click2Dial+

{
  "manifest_version": 2,
  "name": "Asterisk Click2Dial+",
  "version": "0.6",
  "description": "This is an easy to use extention, select any number on a web page, right click to open the context menu which you can use to call this number.",
  "author": "Simone Freddio",
  "icons": {
    "48": "icons/asterisk-48.png"
  },
  "permissions": [
    "storage",
    "menus",
    "<all_urls>",
    "activeTab",
    "tabs"
  ],
  "browser_action": {
    "default_icon": {
      "20": "icons/asterisk-20.png",
      "32": "icons/asterisk-32.png"
    },
    "default_title": "Asterisk Click2Dial+",
    "default_popup": "popup/popupAsterisk.html"
  },
  "options_ui": {
    "page": "options.html"
  },
  "background": {
    "scripts": [
      "asterisk.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content-script.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{49f69da8-c87c-4bf4-a368-520e8833393a}"
    }
  }
}