Examine source code of SubSync Lite

{
  "manifest_version": 3,
  "name": "SubSync Lite",
  "version": "1.0.0",
  "description": "Tiny slider to quickly adjust subtitle timing (delay/advance) by 50–100 ms steps without opening the player's menu.",
  "icons": {
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "permissions": [
    "storage"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "contentScript.js"
      ],
      "css": [
        "styles.css"
      ],
      "run_at": "document_idle"
    }
  ],
  "action": {
    "default_title": "SubSync Lite"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "subsync-lite@example.com",
      "strict_min_version": "91.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}