Add support for conformers

[green-coder]

As suggested by @borkdude, it could be useful to support conformers in Minimallist.

Reference:
https://clojuredocs.org/clojure.spec.alpha/conformer

Use case from @borkdude:
https://gist.github.com/borkdude/6b9c48636b5f9169d26deb13dcfc8ba9