Examine source code of Fastmail Checker

{
  "manifest_version": 3,
  "name": "Fastmail Checker",
  "description": "Fastmail unread checker with badge, sound notifications, and DND.",
  "version": "0.1.5",
  "action": {
    "default_title": "Fastmail Checker",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background/index.js"
    ],
    "type": "module"
  },
  "options_page": "options.html",
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "permissions": [
    "alarms",
    "notifications",
    "storage",
    "contextMenus",
    "identity"
  ],
  "host_permissions": [
    "https://fastmail-checker.mave.me/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "fastmail-checker@mave.me",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}