Add overloaded

include/utempl/overloaded.hpp

@@ -0,0 +1,13 @@
+#pragma once
+#include <utility>
+
+namespace utempl {
+template <typename... Fs>
+inline constexpr auto Overloaded(Fs&&... fs) {
+  struct Overloaded : public std::remove_cvref_t<Fs>... {
+    using Fs::operator()...;
+  };
+  return Overloaded{std::forward<Fs>(fs)...};
+};
+
+} // namespace utempl