Add section for configuration notes with initial note about the default editor

contrib/win32/ReadMe.html

@@ -89,6 +89,10 b' hg'
     <p>This command should print a useful help message.  If it does,
       other Mercurial commands should work fine for you.</p>
 
+    <h1>Configuration notes</h1>
+    <p>The default editor is 'vi'. You can set the EDITOR environment variable
+    (or HGEDITOR) to specify your preference. </p>
+
     <h1>Reporting problems</h1>
 
     <p>Before you report any problems, please consult the <a