Merge pull request #853 from hacspec/mention-playground

feat(README): link playground

README.md

@@ -7,7 +7,8 @@
   <a href="https://hacspec.org/book">📖 Book</a> |
   <a href="https://hacspec.org/blog">📝 Blog</a> |
   <a href="https://hacspec.zulipchat.com/">💬 Zulip</a> |
-  <a href="https://hacspec.org/hax/">🛠️ Internal docs</a>
+  <a href="https://hacspec.org/hax/">🛠️ Internal docs</a> |
+  <a href="https://hax-playground.cryspen.com/">🛝 Playground</a>
 </p>
 
 # Hax
@@ -24,6 +25,12 @@ standard library, to write succinct, executable, and verifiable specifications i
 Rust.
 These specifications can be translated into formal languages with hax.
 
+<p align="center">
+    <a href="https://hax-playground.cryspen.com/#fstar+tc/latest-main/gist=5252f86237adbca7fdeb7a8fea0b1648">
+    Try out hax online now!
+    </a>
+</p>
+
 ## Learn more
 
 Here are some resources for learning more about hax: