[New package] ppx_show 0.1.0 (#14412)
[New package] ppx_show 0.1.0 (#14412)

* [New package] ppx_show 0.1.0

OCaml PPX deriver for deriving `show` based on `ppxlib`.

This library reimplements the `show` plugin from [`ppx_deriving`] as a
`ppxlib` deriver.
In particular, this deriver works with OCaml 4.08.0.

[`ppx_deriving`]: https://github.com/ocaml-ppx/ppx_deriving

* Fix compatibility for OCaml <4.08.0

* Missing depends

* Remove duplicate depends

* Add missing opam fields

* Fix license

fdopen/opam-repository-mingw,fdopen/opam-repository-mingw