Consider Go's new io/fs filesystem interfaces for IPFS

See https://go.googlesource.com/proposal/+/master/design/draft-iofs.md; note that it's just a draft still, and it has a Youtube video presentation as well as a Reddit discussion thread.

It's early days for this idea, but if it does get proposed and accepted, it seems like a great fit for IPFS. Pretty much any package that expects to work with a filesystem could magically be composed on top of IPFS with minimal effort, in theory.

/cc @mikeal @warpfork