implement support for setting indexed values

vm/src/main/kotlin/gay/pizza/pork/vm/StandardOpHandlers.kt

@@ -15,6 +15,7 @@ val StandardOpHandlers: List<OpHandler> = listOf(
   ListSizeOpHandler,
 
   IndexOpHandler,
+  IndexSetOpHandler,
 
   AndOpHandler,
   OrOpHandler,

vm/src/main/kotlin/gay/pizza/pork/vm/ops/IndexSetOpHandler.kt

@@ -0,0 +1,15 @@
+package gay.pizza.pork.vm.ops
+
+import gay.pizza.pork.bytecode.Op
+import gay.pizza.pork.bytecode.Opcode
+import gay.pizza.pork.vm.InternalMachine
+import gay.pizza.pork.vm.OpHandler
+
+object IndexSetOpHandler : OpHandler(Opcode.IndexSet) {
+  override fun handle(machine: InternalMachine, op: Op) {
+    val list = machine.pop<MutableList<Any>>()
+    val index = machine.pop<Number>().toInt()
+    val value = machine.pop<Any>()
+    list[index] = value
+  }
+}

vm/src/main/kotlin/gay/pizza/pork/vm/ops/ListMakeOpHandler.kt

@@ -13,6 +13,6 @@ object ListMakeOpHandler : OpHandler(Opcode.ListMake) {
       val item = machine.popAnyValue()
       list.add(item)
     }
-    machine.push(list.reversed())
+    machine.push(list.reversed().toMutableList())
   }
 }