Examine source code of 24h icon

{
  "manifest_version": 2,
  "name": "24h icon",
  "version": "1.0",
  "description": "The 24-hour symbol is often used to represent a service that operates continuously around the clock, without breaks.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html",
    "default_title": "Click me!"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ed3079d4-4a1f-4fb1-8c28-fbe31890ccc0}"
    }
  }
}