Add Netstratum link to users page (#380)

Author: vishnutasok333

src/pages/users.mdx

@@ -54,6 +54,7 @@ mailing list <b>users@cloudstack.apache.org</b>.
 - [Miriadis](http://www.miriadis.com)
 - [Neobitti](http://neobitti.fi)
 - [NetPoint](https://netpoint-dc.com/)
+- [Netstratum](https://netstratum.com/)
 - [NxtGen Cloud Technologies Private Limited](https://nxtgen.com)
 - [Openminds](http://www.openminds.be)
 - [Overweb srl](http://stacksquare.com)