Make clear that names/values are UTF-8 in x-www-form-urlencoded

[jogu]

Mirrors text used in https://datatracker.ietf.org/doc/html/rfc6749#appendix-B

closes #40

[jogu]

Wouldn't it make sense to introduce the general encoding scheme somewhere in terminology with most of the original text you linked and then reference to it?

MUST be encoded using the UTF-8 character encoding scheme [RFC3629] first; the resulting octet sequence then needs to be further encoded using the escaping rules defined in [W3C.REC-html401-19991224].

Thanks Christian. I'm not sure if I want to start picking at some of that as things start to unravel/get more complicated. The RFC6749 definition isn't actually the canonical one anymore - the definition of application/x-www-form-urlencoded as per the official media type registration ( https://www.iana.org/assignments/media-types/application/x-www-form-urlencoded ) is actually found in https://url.spec.whatwg.org/#application/x-www-form-urlencoded but that's a pretty hard definition to read... and the important thing is basically "you can just use what the url/http library in your favourite language already does but do make sure to use utf-8 as that's the only part that's really not defined elsewhere".

[nemqe]

In general I would just remove the word first from the sentences because in the referred section there is a continuation (first encode it using utf-8, then escape it) and here we are missing that so it reads a bit funny (at least to me, but I am not a native speaker).

[Sakurann]

I tend to agree with @nemqe 's suggetion to remove first. and the direction to clarify things as they are in this PR vs introducing a new section

[jogu]

Thanks for the feedback, and to Kristina for adding the suggestions - I've committed them, please review/approve!