Add message for GHC-72771 "Mismatched default method signature"

[VeryMilkyJoe]

No description provided.

[Bodigrim]

Let's link a stable released documentation instead of GitLab:

Suggested change

	This error means that there is a type class with some method `m` for which a [default signature](https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/default_signatures.html) was defined, but that default signature does not match the type signature of `m`.
	This error means that there is a type class with some method `m` for which a [default signature](https://downloads.haskell.org/ghc/9.12.1/docs/users_guide/exts/default_signatures.html) was defined, but that default signature does not match the type signature of `m`.

[Bodigrim]

1. If you rename it to module Lib where there would be no need to define main :: IO (), minimizing the example.

2. Let's add {-# LANGUAGE TypeOperators #-}, otherwise recent GHCs throw a warning about ~.

3. Could we please rename Enum -> Enumerate, enum -> enumerate? So that we do not clash with a usual class Enum from Prelude.