Replace Matrix link with Zulip link

Author: CookieSource

src/content/docs/index.mdx

@@ -16,9 +16,9 @@ hero:
       link: https://github.com/aerynos/dotdev
       icon: github
       variant: primary
-    - text: Matrix
-      link: https://matrix.to/#/#aerynos:matrix.org
-      icon: matrix
+    - text: Zulip
+      link: https://aerynos.zulipchat.com/join/fuqokhsomj5mzqj6akqaiqlr/
+      icon: zulip
       variant: primary
     - text: Forums
       link: https://github.com/orgs/AerynOS/discussions