ESM/browser support

[felixfbecker]

I'd love to use this package in the browser, but currently it uses Node-style CommonJS. Would it be possible to support ESM through package.json fields?

[dougwilson]

I am fine to add more platforms than Node.js if that does not end up forking the code too much. If someone would like to put a pull request together that adds said support and includes the appropriate tests that back up whatever the platform is in the CI. It sounds like you said web browser, so we'd want to make sure some kind of web browser test matrix is added to the CI with it.

[KostyaTretyak]

@felixfbecker, try @ts-stack/type-is. This is a fork of type-is, but this one accepts headers instead of a request object. Writen in TypeScript in format ESM.