Add calculated Content-Type header in HTTPResponse

[gulivero1773]

Need add calculated Content-Type header in HTTPResponse because if need add Content-Type in response then need add it into swiftopenapi.yaml file, but it it is to many options of Content-Type header. On image exist only some of many

[guoye-zhang]

Media type is not specific to HTTP. On Darwin it is handled by UniformTypeIdentifiers framework. I think it might be better as a separate package.

[Saklad5]

I think it's best that we don't try to replace IANA's registry here. Perhaps just include a link to that in the documentation?