Examine source code of Softphone Extension

{
  "manifest_version": 3,
  "name": "Softphone Extension",
  "description": "Chromium extension for use with our Softphone application",
  "version": "1.0",
  "browser_specific_settings": {
    "gecko": {
      "id": "firefoxextension@voicehost.co.uk"
    }
  },
  "content_scripts": [
    {
      "all_frames": true,
      "js": [
        "helper.js",
        "country_prefix.js",
        "script.js"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "images/*"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "permissions": [
    "storage",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_popup": "pages/index/index.html"
  },
  "options_ui": {
    "open_in_tab": true,
    "page": "pages/options/options.html"
  },
  "icons": {
    "16": "images/icon-16.png",
    "48": "images/icon-48.png",
    "128": "images/icon-128.png"
  }
}