Examine source code of LoopTube

{
  "name": "LoopTube",
  "version": "1.2.1",
  "manifest_version": 3,
  "description": "Adds loop button inside YouTube player controls",
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "looptube@shalin.dev",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "action": {
    "default_title": "LoopTube",
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "48": "icons/icon48.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*",
        "*://m.youtube.com/*",
        "*://youtu.be/*"
      ],
      "css": [
        "style.css"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  }
}