Examine source code of Voipfone Browser Calls

{
  "manifest_version": 2,
  "name": "Voipfone Browser Calls",
  "homepage_url": "https://www.voipfone.co.uk",
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "64": "icons/icon64.png",
    "128": "icons/icon128.png",
    "256": "icons/icon256.png"
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "contextMenus",
    "storage",
    "tabs",
    "webRequest",
    "webRequestBlocking",
    "https://api.voipfone.co.uk/v1/",
    "https://controlpanel.voipfone.co.uk/"
  ],
  "applications": {
    "gecko": {
      "id": "@voipfonebrowsercalls"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "linkify.js"
      ]
    }
  ],
  "description": "Converts telephone numbers into links that can be clicked to place a call using the Voipfone callback service.",
  "version": "6.0.0"
}