Add "Demo" link for Cactus Comments

README.md

@@ -425,7 +425,7 @@ _[SIP](https://en.wikipedia.org/wiki/Session_Initiation_Protocol)/[IPBX](https:/
 - [Bootcamp](http://trybootcamp.vitorfs.com) - Enterprise social network. ([Source Code](https://github.com/vitorfs/bootcamp)) `MIT` `Python`
 - [Buddycloud](http://buddycloud.com/) - Tools, libraries, services and a community to build user-to-user, group and social messaging into your app. Saves time. Scales up. Supports you. ([Source Code](https://github.com/buddycloud)) `Apache-2.0` `Java`
 - [BuddyPress](https://buddypress.org/about/) - Powerful plugin that takes your WordPress.org powered site beyond the blog with social-network features like user profiles, activity streams, user groups, and more. ([Source Code](https://github.com/buddypress/BuddyPress)) `GPL-2.0` `PHP`
-- [Cactus Comments](https://cactus.chat/) - Cactus Comments is a federated comment system for the open web built on Matrix. ([Source Code](https://gitlab.com/cactus-comments/)) `GPL-3.0` `Python`
+- [Cactus Comments](https://cactus.chat/) - Cactus Comments is a federated comment system for the open web built on Matrix. ([Demo](https://cactus.chat/demo/), [Source Code](https://gitlab.com/cactus-comments/)) `GPL-3.0` `Python`
 - [cartulary](https://github.com/daveajones/cartulary) - RSS reader, readability tool, article archiver, microblogger, social graph manager and reading list manager. `CDDL-1.0` `PHP`
 - [Commento](https://gitlab.com/commento/commento) - Commento is a discussion platform that you can embed on your blog, news articles, and any place where you want your readers to add comments. `MIT` `GO`
 - [Coral](https://coralproject.net/) - A better commenting experience from Vox Media. ([Source Code](https://github.com/coralproject/talk)) `Apache-2.0` `Nodejs`