Add help reference

README.md

@@ -28,6 +28,9 @@ Available subcommands:
 * `volume`
 * `zone`
 
+Note that right now, only getting data through the `list/` endpoints is supported.
+See section help for more details, i.e.: `lunanode image help`
+
 ## TODO (looking for contributors)
 
 * [ ] Simplify code so there is less boilerplate. In particular, writing out every enum variant is pretty annoying when I need the same info out of them either way.