Add private beta note to Volumes overview page (#177)

Author: dobrac

docs/volumes.mdx

@@ -3,6 +3,11 @@ title: "Volumes"
 sidebarTitle: Overview
 ---
 
+<Note>
+Volumes are currently in private beta.
+If you'd like access, please reach out to us at [[email protected]](mailto:[email protected]).
+</Note>
+
 Volumes provide persistent storage that exists independently of sandbox lifecycles. Data written to a volume persists even after a sandbox is shut down, and volumes can be mounted to multiple sandboxes over time.
 
 **One volume shared across multiple sandboxes**