HTTP client (requests) in stdlib

[jiribenes]

It would be amazing to have some HTTP request support in our stdlib, at least in the jsWeb and jsNode backends.
This would unlock a bunch of cool use cases (APIs!) with cool effects.

Feel free to take a look at my experiment in #720, it might be a good starting point.

[marzipankaiser]

One attempt is started #1020 (works on js and node AFAICT)