`max_v` should be moved outside of `detail`

[Ambeco]

max_v is very useful, but seems "private" inside of the detail namespace. IMO, it should be moved out.
Also, it's enum_subtype S template parameter should default to = subtype_v<E>.

It is less clear if min_v is equally value, but for symmetry, should probably also be made "public". Alternatively, expose a range_v<E> that returns the range min_v to max_v.

These are handy for helper code that map enum values to other things, such as in https://stackoverflow.com/a/79981587/845092

[Neargye]

Hi @Ambeco,
Instead of exposing the internal min_v and max_v, what about adding public functions that return the max/min enum values?

constexpr auto min = magic_enum::enum_min<MyEnum>();
constexpr auto max = magic_enum::enum_max<MyEnum>();

// impl
template <typename E, detail::enum_subtype S = detail::subtype_v<E>>
[[nodiscard]] constexpr auto enum_max() noexcept -> detail::enable_if_t<E, std::decay_t<E>> {
  using D = std::decay_t<E>;
  static_assert(detail::count_v<D, S> > 0, "magic_enum::enum_max requires at least one reflected enum value.");

  return detail::values_v<D, S>.back();
}

They would return MyEnum, use the default enum subtype, and also support an explicit subtype:

magic_enum::enum_max<MyEnum, magic_enum::as_flags<>>();

The underlying value would still be available through enum_underlying(max). This keeps the internal variables private and follows the existing function-based API.