add spelunking index entry

systems.tex

@@ -14,10 +14,10 @@
 A tie could indicate that the door has a massive hole in the middle, allowing a sufficiently small person to squeeze through; or it might indicate that the door caves in after multiple, noisy strikes.
 
 \makeRule{excavation}{Excavation}{Strength}{Caving}{depends on the type of rock}
+\index{Spelunking!Excavation}
 
 \subsection{Downtime Activities}
 
-
 \makeRule{poison}{Brewing a poison}{Intelligence}{Medicine}{4}
 \index{Poisons}