fixed header including for std::nullopt_t, in gcc

hedzr · hedzr · commit fbdf26c7d72e · 2023-03-26T12:16:22.000+08:00
diff --git a/include/fsm_cxx/fsm-sm.hh b/include/fsm_cxx/fsm-sm.hh
@@ -38,6 +38,7 @@
 // #include <initializer_list>
 // #include <list>
 // #include <map>
+#include <optional>
 // #include <set>
 #include <unordered_map>
 #include <vector>
