middleware: add Discard method to WrapResponseWriter (go-chi#926)

* middleware: add Discard method to WrapResponseWriter

* resolve review comments

* use ioutil.Discard and deprecate the public interface

* move the Discard method back to the public interface

* discard calls to WriteHeader too

Revert "fix(middleware): Close created writer in the compressor middl…

…eware (#…" (go-chi#924)

This reverts commit f10dc4a.

fix(middleware): Close created writer in the compressor middleware (g…

…o-chi#919)

Deprecate github.com/go-chi/chi v4 module

Deprecate github.com/go-chi/chi v3 module

Deprecate github.com/go-chi/chi v2 module

Deprecate github.com/go-chi/chi v1 module