Publish TypeScript types for the polyfill packages

Hi, and thank you for maintaining these polyfill packages.

Could you consider publishing TypeScript types for them?

In particular, having types available would make it easier to integrate `@babel/helper-define-polyfill-provider` in TypeScript projects. At the moment, consumers may need to add their own declarations or work around missing type information when configuring a provider around these polyfills.

Thank you for considering this.

Start by inventorying the polyfill packages and reading how @babel/helper-define-polyfill-provider is configured for consumers. Determine which public APIs need declarations and how types should be published with the packages. Done means TypeScript consumers can configure the provider without adding their own declarations or working around missing type information.

Written by the indexing model from the issue text.