add litefs deployment to the example

[tantaman]

if we're going to do this it is unclear if we can actually use the websocket server.

The reason is that writes to litefs must go to the primary. litefs supports a proxy (https://fly.io/docs/litefs/proxy/) to route non-get requests to the primary.

If we're on websocket, however, we can't use this (from what I can tell so far).

[tantaman]

Looks like we can check this file before issuing our write in the websocket server:

https://fly.io/docs/litefs/primary/

There is also this: https://github.com/superfly/litefs/issues/56

but apparently it isn't good for cases with a high write volume.

[tantaman]

This'll need to wait on LiteFS support in the Vulcan websocket server -- https://github.com/vlcn-io/js/pull/7