Examine source code of Facebook Messenger Flash

{
  "manifest_version": 3,
  "name": "Messenger Taskbar Flash",
  "version": "1.0.0",
  "description": "Unofficial add-on that flashes the Firefox Messenger web-app taskbar button for new unread messages.",
  "icons": {
    "32": "icons/taskbar-flash.svg",
    "48": "icons/taskbar-flash.svg",
    "64": "icons/taskbar-flash.svg",
    "96": "icons/taskbar-flash.svg",
    "128": "icons/taskbar-flash.svg"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "host_permissions": [
    "https://messenger.com/*",
    "https://www.messenger.com/*",
    "https://www.facebook.com/messages/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://messenger.com/*",
        "https://www.messenger.com/*",
        "https://www.facebook.com/messages/*"
      ],
      "js": [
        "detector.js",
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{a9c86b1e-1749-4e85-bc44-b5e13c780eb6}",
      "strict_min_version": "143.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}