feature: added information about OpenResty's commercial support in the default index.html page.

Signed-off-by: Yichun Zhang (agentzh) <agentzh@gmail.com>

html/index.html

@@ -16,7 +16,9 @@
 working. Further configuration is required.</p>
 
 <p>For online documentation and support please refer to
-<a href="https://openresty.org/">openresty.org</a>.<br/></p>
+<a href="https://openresty.org/">openresty.org</a>.<br/>
+Commercial support is available at
+<a href="https://openresty.com/">openresty.com</a>.</p>
 
 <p><em>Thank you for flying OpenResty.</em></p>
 </body>