add Zulip to supporters

Author: TimidRobot

content/community/supporters/contents.lr

@@ -72,10 +72,12 @@ will no longer hold their standards ransom for a purchase fee.
 - [Outreachy][outreachy]
 - [PagerDuty for Nonprofits][pagerduty]
 - [UptimeRobot][uptimerobot]
+- [Zulip][zulip]
 
 [cloudflare]: https://www.cloudflare.com/galileo/
 [github]: https://socialimpact.github.com/
 [gsoc]: https://summerofcode.withgoogle.com/
 [outreachy]: https://www.outreachy.org/
 [pagerduty]: https://www.pagerduty.com/industries/non-profit/
 [uptimerobot]: https://uptimerobot.com/
+[zulip]: https://zulip.com/