Merge pull request #1622 from ericniebler/add-missing-include-chrono

timed_scheduler.hpp needs to #include <chrono> for system_clock

Author: ericniebler

include/exec/timed_scheduler.hpp

@@ -18,6 +18,8 @@
 
 #include "../stdexec/execution.hpp"
 
+#include <chrono>
+
 namespace exec {
   namespace __now {
     using namespace stdexec;