sensorcommands: add optional header

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: If1883c74aadcedff7a17ba84f03cc058589f3612
diff --git a/src/sensorcommands.cpp b/src/sensorcommands.cpp
index b2490d5..effd0f5 100644
--- a/src/sensorcommands.cpp
+++ b/src/sensorcommands.cpp
@@ -24,6 +24,7 @@
 #include <ipmid/api.hpp>
 #include <ipmid/utils.hpp>
 #include <map>
+#include <optional>
 #include <phosphor-logging/log.hpp>
 #include <sdbusplus/bus.hpp>
 #include <sdrutils.hpp>