Support httpx2

[honzajavorek]

TIL that httpx2 exists https://httpx2.pydantic.dev/ and unlike httpx, it has active development and security fixes. I'm migrating my projects to it and just thought that it might be a good idea for githubkit as well.

[Patchouli-CN]

umm，hello? I want to handle it. did @yanyongyu already do this?