MSVC fails to compile std::swap specialization for nlohmann::json

[NotAPenguin0]

• What is the issue you have?
  When compiling a project using the library, MSVC throws an error:
  no instance of overloaded std::swap matches the specified type.

• Please describe the steps to reproduce the issue. Can you provide a small but working code example?
  Any program using the library and compiling with MSVC.

• What is the expected behavior?
  It should compile (as clang and gcc accept it), even though it is nonstandard.

• And what is the actual behavior instead?
  It fails to compile

• Which compiler and operating system are you using? Is it a supported compiler?
  MSVC 15.6 with C++17 enabled on Windows 10

• Did you use a released version of the library or the version from the develop branch?
  develop

Suggested fix: It should be a specialization, not an overload. This way it compiles on MSVC, and still compiles with clang and gcc:

namespace std
{
    template<>
    inline void swap<nlohmann::json>(nlohmann::json& first, nlohmann::json& second) noexcept(
		is_nothrow_move_constructible<nlohmann::json>::value &&
		is_nothrow_move_assignable<nlohmann::json>::value
		)
        
    {
        first.swap(second);   
    }

}

[nlohmann]

Fixed. Thanks for reporting!