Add links to public Zulip channel from Github and Dafny web sites. (#…

…6039)

README.md

@@ -27,7 +27,7 @@ A reference manual is available both [online](https://dafny-lang.github.io/dafny
 
 ## Community
 
-You can ask questions about Dafny on [Stack Overflow](https://stackoverflow.com/questions/tagged/dafny) or participate in general discussion on Dafny's [![Gitter](https://badges.gitter.im/dafny-lang/community.svg)](https://gitter.im/dafny-lang/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge).
+Feel free to report issues here on GitHub or to ask for questions on our :speech_balloon: [Zulip](https://dafny.zulipchat.com/) channel. 
 
 ## Try Dafny
 

docs/index.html

@@ -31,6 +31,7 @@ <h2>Quick Links</h2>
 <ul>
 <li><a href="./Installation"><b>Installation</b></a>
      (or a <a href="https://marketplace.visualstudio.com/items?itemName=dafny-lang.ide-vscode">VSCode plugin for Dafny</a>)</li>
+<li><a href="https://dafny.zulipchat.com/" target="_blank" rel="noopener noreferrer">Zulip channel</a> to ask questions about Dafny</li>
 <li><a href="./DafnyRef/DafnyRef">Dafny Reference Manual and User Guide</a></li>
 <li><a href="./toc">Dafny Resources for Users</a></li>
 <li><a href="https://github.com/dafny-lang/dafny">Dafny GitHub project (for developers of the Dafny tools themselves)</a></li>