update README.md.

README.md

@@ -6,9 +6,17 @@ For example, you can create ".well-known/acme-challenge" in skin folder.
 Next, you need to provide Zope's username and password in ~/.netrc like :
 
 ```text
+machine www.example.com
+login zope_username
+password zope_password
+
 machine example.com
 login zope_username
 password zope_password
+
+machine another.example.com
+login zope_username
+password zope_password
 ```
 
 You need to prepare "config" file like :