Examine source code of Mini World Clock

{
  "manifest_version": 3,
  "name": "Mini World Clock",
  "short_name": "World clock",
  "version": "0.0.6",
  "description": "Mini clock for several time zones",
  "action": {
    "default_popup": "index.html",
    "default_icon": {
      "16": "assets/clock_icon.png",
      "48": "assets/clock_icon.png",
      "128": "assets/clock_icon.png"
    }
  },
  "icons": {
    "16": "assets/clock_icon.png",
    "48": "assets/clock_icon.png",
    "128": "assets/clock_icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "w_c_e@obayomi.com",
      "strict_min_version": "58.0"
    },
    "safari": {
      "strict_min_version": "14",
      "strict_max_version": "20"
    }
  }
}