Added a basic creatable loop object with PID control (#1141)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

src/bacnet/property.c

@@ -1851,6 +1851,7 @@ static const int Loop_Properties_Optional[] = {
     /* unordered list of properties */
     PROP_DESCRIPTION,
     PROP_RELIABILITY,
+    PROP_UPDATE_INTERVAL,
     PROP_PROPORTIONAL_CONSTANT,
     PROP_PROPORTIONAL_CONSTANT_UNITS,
     PROP_INTEGRAL_CONSTANT,