Add bad numbers for script dataset mistake to errata

Issue marijnh#485

Author: marijnh

05_higher_order.md

@@ -551,7 +551,7 @@ for (let script of SCRIPTS) {
   }
 }
 console.log(Math.round(total / count));
-// → 1188
+// → 1165
 ```
 
 But it is harder to see what was being computed and how. And because

html/errata.html

@@ -30,6 +30,14 @@ <h2>Chapter 2</h2>
 <p><strong>Page 34</strong> (1st) <em>Updating Bindings Succintly</em>: Where it
 says <code>counter-</code> it should be <code>counter--</code>.</p>
 
+<h2>Chapter 5</h2>
+
+<p><strong>Page 91</strong> <em>Composability</em>: Due to an initial
+mistake in the script data set, the results of the computations on
+this page differ from the ones with the current, corrected data. The
+average year for living scrips should be 1165, the average for
+non-living scripts should be 204.</p>
+
 <h2>Chapter 6</h2>
 
 <p><strong>Page 111</strong> (2nd) <em>Inheritance</em>: In the second