Allow the `await` keyword at the top-level within JavaScript modules.
Allows more seamless integration of async calls into the module loading process. Today this is accomplished by wrapping modules in async functions, but this pushes complexity into dependent modules and exposes implementation details.
Docs: https://docs.google.com/document/d/15jxKo7kqj0bRHcnSmwjhj1XaWH1AXRDtYPiJHluCSiA/edit
Samples: See design doc.
Explainers: https://v8.dev/features/top-level-await https://github.com/tc39/proposal-top-level-await