Update feed URL to reference main

Fixes #43
See publicsuffix/list#1348

list/index.html

@@ -47,7 +47,7 @@ <h2>
             <a href="public_suffix_list.dat">See the list</a>
         </div>
         <p>
-            To be kept informed of changes to the list, you can subscribe to an <a href="https://github.com/publicsuffix/list/commits/master.atom">Atom change feed</a> in your favourite feed reader.
+            To be kept informed of changes to the list, you can subscribe to an <a href="https://github.com/publicsuffix/list/commits/main.atom">Atom change feed</a> in your favourite feed reader.
         </p>
         <h2 id="list-format">
             List format