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/lovecraft.wren

@@ -0,0 +1,9 @@
+import "cthulu" for Cthulu
+
+class Lovecraft {
+    say {
+        return (new Cthulu).message
+    }
+}
+
+IO.print((new Lovecraft).say)