config/core: include cstdint also when ENTT_ID_TYPE is defined

src/entt/config/config.h

@@ -28,7 +28,6 @@
 #endif
 
 #ifndef ENTT_ID_TYPE
-#    include <cstdint>
 #    define ENTT_ID_TYPE std::uint32_t
 #endif
 

src/entt/core/fwd.hpp

@@ -1,6 +1,7 @@
 #ifndef ENTT_CORE_FWD_HPP
 #define ENTT_CORE_FWD_HPP
 
+#include <cstdint>
 #include <type_traits>
 #include "../config/config.h"