Fix edition number on front page

Author: marijnh

html/index.html

@@ -27,7 +27,7 @@
     </a>
   </p>
 
-  <h1>Eloquent JavaScript<div style="font-size: 70%">3rd edition (2018)</div></h2>
+  <h1>Eloquent JavaScript<div style="font-size: 70%">4th edition (2024)</div></h2>
 
   <p>This is a book about JavaScript, programming, and the wonders of
   the digital. You can read it online here, or buy your own