Remove dependency on pkg-config

[lapinozz]

pkg-config doesn't seem to be actually used for anything
it's simpler to use find_package() just like for the other libraries

[prince-chrismc]

What release was official cmake targets export by wolfssl? Do this require an update to the CI for what versions are tested against?

[lapinozz]

What release was official cmake targets export by wolfssl?

I don't understand the question

Do this require an update to the CI for what versions are tested against?

I'm not sure, I haven't checked the CI, I only tested to compile locally in static and shared build

I would just be a nice improvement since pck-config is an additional dependency and VS/MSVC doesn't come with it

[Thalhammer]

I am unsure if the official wolfssl distribution comes with cmake targets.
However even if it doesn't it might be worth it instead provide a FindWolfSSL.cmake file within the jwt-cpp repo and dropping pkg-config.