Examine source code of Stop FB Auto-Refresh

{
  "manifest_version": 3,
  "name": "Stop FB Auto-Refresh",
  "version": "1.0",
  "description": "Prevents Facebook from automatically refreshing your feed when switching tabs or apps.",
  "browser_specific_settings": {
    "gecko": {
      "id": "stop-fb-autorefresh@myextension.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "activeTab"
  ],
  "icons": {
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.facebook.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start",
      "world": "MAIN"
    }
  ]
}