Guide on how to create a ReScript lib for JS usage

It would be great if we'd document how to set up a ReScript project, so that it is publishable on npm without any dependency to the ReScript compiler toolchain.

I know that some workflows are blocked by the fact that ReScript doesn't ship an independent precompiled stdlib / belt package, but others have reported that a rollup based workflow is also viable as well.

Would be interesting to create a dedicated page for a rollup based setup, just to bridge the gap until we see how ppl are getting along with shipping ReScript based JS libs.