Examine source code of PNG Transparency Checker

{
  "manifest_version": 2,
  "name": "PNG Transparency Checker",
  "version": "1.0",
  "description": "Checks if an image is a true PNG with a transparent background.",
  "permissions": [
    "contextMenus",
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "contact@somar-kesen.com",
      "strict_min_version": "55.0"
    }
  }
}