Examine source code of Accessibility Checker

{
  "manifest_version": 2,
  "name": "Accessibility Checker",
  "version": "1.0",
  "description": "Check web page accessibility issues quickly.",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{49b787df-5e33-4735-9567-459af7ba943a}"
    }
  }
}