allow pyscript.fetch to be separately awaited

[WebReflection]

As soon as we released the simplified pyscript.fetch API of course users wanted to do more with it and that's OK.

The issue is that we just provide a single point of await with current utility, but in an ideal world we should be able to grant both the shortcut and the response expectations, just like the module inspiring current API does: https://github.com/WebReflection/fetch#readme

I am not sure how Python can (or can it?) handle this dual facades of the same underlying pipe, but I believe if it's possible in JS it gotta be possible in Python too!

This issue is to make the current utility be able to do both:

from pyscript import fetch

json = await fetch(url).json()
response = await fetch(url)
if response.ok:
  await response.json()

If anyone would like to share thoughts or tricks to make this possible, I am all ears!

/cc @JeffersGlass @antocuni

[WebReflection]

closing as this got merged addressing all concerns and allowing await fetch(...) a part.