add disk-cache to server config, for S3 dbs

Author: refset

src/clj/xt_play/config.clj

@@ -3,5 +3,5 @@
 (def pgwire-port 5432)
 
 (def node-config
-  {:server
-   {:port pgwire-port}})
+  {:server {:port pgwire-port}
+   :disk-cache {:path "/tmp/xtdb-cache"}})