Examine source code of RTL Page Fixer

{
  "manifest_version": 2,
  "name": "RTL Page Fixer",
  "version": "1.1",
  "description": "Apply RTL to current page only",
  "browser_specific_settings": {
    "gecko": {
      "id": "rtl-fixer@yourdomain.com",
      "strict_min_version": "79.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  },
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icons/icon-48.png",
    "default_title": "Apply RTL to Current Page",
    "default_popup": "popup/popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content-script.js"
      ],
      "css": [
        "content-style.css"
      ],
      "run_at": "document_idle"
    }
  ]
}