Fix a small mistake in Chapter 20

And add an errata.

Author: marijnh

20_node.md

@@ -1128,7 +1128,7 @@ way to _create_ a ((directory)).
 
 {{index "MKCOL method", "mkdir function"}}
 
-Add support for the `MKCOL` method ("make column"), which should create
+Add support for the `MKCOL` method ("make collection"), which should create
 a directory by calling `mkdir` from the `fs` module. `MKCOL` is not a
 widely used HTTP method, but it does exist for this same purpose in
 the _((WebDAV))_ standard, which specifies a set of conventions on top

html/errata.html

@@ -27,4 +27,9 @@ <h2>Chapter 2</h2>
 <p><strong>Page 34</strong> (Updating Bindings Succintly): Where it
 says <code>counter-</code> it should be <code>counter--</code>.</p>
 
+<h2>Chapter 20</h2>
+
+<p><strong>Page 369</strong> (Directory Creation): `MKCOL` stands for
+"make collection", not "make column" as the book claims.</p>
+
 </article>