Examine source code of Ringfree BrowserDial

{
  "manifest_version": 2,
  "name": "Ringfree BrowserDial",
  "version": "1.0.1resigned1",
  "description": "Enables Ringfree BrowserDial on most web pages. Simply click a phone number link (or \"tel\" link in web speak) and it'll initiate a call between your extension and that number. Automatic answering on your extension can optionally be enabled for supported SIP clients such as desk phones and softphones.\n\nThis extension requires active phone service through Ringfree Communications Inc. To obtain API credentials please contact your Ringfree Customer Success Manager or your IT service provider.\n\n© 2018 Ringfree Communications Inc. Code available under the terms of the MIT License, a copy of which is included with this extension. All Ringfree brand features (logos, icons, images, etc) are © 2018 Ringfree Communications Inc. All rights reserved.",
  "icons": {
    "32": "icons/rf-logo-32.png",
    "48": "icons/rf-logo-48.png",
    "96": "icons/rf-logo-96.png",
    "128": "icons/rf-logo-128.png",
    "256": "icons/rf-logo-256.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "jquery-3.2.1.min.js",
        "browserDial.js"
      ]
    }
  ],
  "options_ui": {
    "page": "options.html"
  },
  "permissions": [
    "storage",
    "https://*.ringfree.biz/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8f053985-47ab-42fd-844f-c67143c6d9bb}"
    }
  }
}