Examine source code of World Clock Pro

{
  "manifest_version": 2,
  "name": "World Clock Pro",
  "version": "1.0.0",
  "description": "Display multiple time zones simultaneously. Pick from 28 cities. Shows current time, date, and offset from your local time.",
  "browser_specific_settings": {
    "gecko": {
      "id": "{86907f09-6df7-4074-adaa-900c1d189eda}",
      "strict_min_version": "96.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "browser_action": {
    "default_icon": {
      "16": "res/icon16.png",
      "32": "res/icon32.png",
      "48": "res/icon48.png",
      "96": "res/icon96.png",
      "128": "res/icon128.png"
    },
    "default_title": "Global Time",
    "default_popup": "code/popup.html"
  },
  "icons": {
    "16": "res/icon16.png",
    "32": "res/icon32.png",
    "48": "res/icon48.png",
    "96": "res/icon96.png",
    "128": "res/icon128.png"
  },
  "permissions": [
    "storage"
  ]
}