Add hint to index.html

index.html

@@ -27,6 +27,10 @@
   <script type="text/javascript" src="highlight.min.js"></script>
   <script type="text/javascript" src="target/scala-2.13/fj-typeinference-fastopt/main.js"></script>
   <br/>
+  <p>
+      Hint: The type inference algorithm processes one class at a time and starts with the first declared class.
+      Classes can therefore only use methods from classes declared before them.
+  </p>
   <p>Credit: the CSS style sheet of this page was shamelessly stolen from <a href="https://github.com/LPTK/simple-algebraic-subtyping">the Simple-sub demo page</a>.</p>
   </body>
 </html>