Add parse-stream call

[Deraen]

Before commit 1cdc4a3 parse-string used to work with InputStream thanks to reflection. Now, parse-string only works with String, which makes sense.

I think it would be good idea to add parse-stream, similar to parse-string but with InputStream type hint.

And related to this, in addition to generate-string, generate-stream taking a writer would be useful.

I just inlined these version to Muuntaja for now: https://github.com/metosin/muuntaja/pull/94/files

[slipset]

I guess a PR would be welcome?