[CodeSandbox]resolve. 「Uncaught ReferenceError: regeneratorRuntime is not defined」

if you download zip from codesandbox and run start with yarn start,
this error occur 「Uncaught ReferenceError: regeneratorRuntime is not defined」in browser

yarn add --dev babel-polyfill

write code in entrypoint file, mabey 「src/index.ts」

import "babel-polyfill"