Examine source code of VIPTel Click

{
  "name": "VIPTel Click",
  "description": "Allows you to call any number located on any web page using VIPTel services and compatible phones or PBX.",
  "version": "2.95",
  "permissions": [
    "activeTab",
    "contextMenus",
    "storage",
    "*://pbxmanager.viptel.sk/*",
    "*://*.pbxmanager.viptel.sk/*"
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "background": {
    "scripts": [
      "main.js"
    ]
  },
  "icons": {
    "48": "images/logo.png"
  },
  "homepage_url": "https://www.viptel.sk/",
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "jid1-fognnghVzIL4VQ@jetpack"
    }
  }
}