Update ContentAPI

ContentAPI.md

@@ -11,3 +11,20 @@ import api.*
 All of the methods are documented and globally accessible. You can use the methods by simply typing their name, e.g. `sendMessage(player, "Bababooey")`. 
 
 It's very important that you read the documentation for the methods you use and attempt to understand them.
+
+Here's an example of a [listener](writing-listeners) that uses the ContentAPI:
+
+```kt
+    override fun defineListeners() {
+        onUseWith(IntType.ITEM, evilTurnip, knife) { player, used, with ->
+            if(removeItem(player, used.asItem())) {
+                sendMessage(player, "You carve a scary face into the evil turnip.")
+                sendMessage(player, "Wooo! It's enough to give you nightmares.")
+                return@onUseWith addItem(player, carvedEvilTurnip)
+            }
+            return@onUseWith false
+        }
+    }
+```
+
+In this example, `sendMessage`, `removeItem` are both ContentAPI methods.