Add support for type parameters

[pke]

As per spec https://www.rfc-editor.org/rfc/rfc9110#section-12.5.1-14 this is valid:

Accept: text/*, text/plain, text/plain;format=flowed, */*

This library does not seem to have a way to extract the format parameter, does it? Would that be something the lib should support or is that out of scope and should be a separate package?