feat: add example demonstrating module import with Cthulu and Lovecraft classes

Add two new Wren source files under example/import-module/ showing how to import and use a module. The cthulu.wren file defines a Cthulu class with a message method returning a Lovecraftian phrase, while lovecraft.wren imports the Cthulu class, instantiates it, and prints the message via IO.print.

example/import-module/cthulu.wren

@@ -0,0 +1,5 @@
+class Cthulu {
+    message {
+        return "Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn"
+    }
+}