scheduler: forgot to add the fwd file to the previous commit :)

src/entt/process/fwd.hpp

@@ -1,13 +1,18 @@
 #ifndef ENTT_PROCESS_FWD_HPP
 #define ENTT_PROCESS_FWD_HPP
 
+#include <cstdint>
+
 namespace entt {
 
 template<typename, typename>
 class process;
 
-template<typename>
-class scheduler;
+template<typename = std::uint32_t>
+class basic_scheduler;
+
+/*! @brief Alias declaration for the most common use case. */
+using scheduler = basic_scheduler<>;
 
 } // namespace entt