Examine source code of Image Highlighter

{
  "manifest_version": 2,
  "name": "Image Highlighter",
  "version": "1.0.0",
  "description": "Quickly count and toggle a visible highlight around every image on the page. No remote code and only minimal permissions.",
  "icons": {
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_action": {
    "default_title": "Image Highlighter",
    "default_popup": "popup.html",
    "default_icon": "icons/icon48.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "image-highlighter@example.com"
    }
  }
}