Serializing numbers

[jakearchibald]

https://url.spec.whatwg.org/#serialize-an-integer - I'm going to do something similar to this in the Fetch spec, for adding numbers to a header.

Feels like something infra should take care of.

It might become part of #193.

[annevk]

Thanks for opening a tracking issue. The URL and Fetch case are slightly different as URL wants a string and Fetch wants a byte sequence.

This should be easier to fix once we have #87 in place.

[jakearchibald]

In Fetch I'm treating it as if it returns a string, since that's what I imagine we'll end up with. UTF-8 encoding turns the string into a byte sequence.