Feature request: add configuration for a startup function #5

While there are hooks and middleware and keybindings, those are not really the "right" place to put code that a user might want to execute as part of starting up a REPL.

For example, I like to define an uptime fn in the user ns, so I can quickly see how long I've had a particular REPL running. For now, I have this code in the existing hooks.clj example file but that feels "wrong".

Could you add a configuration key that takes a qualified symbol, which is executed once at server startup? Perhaps :init-fn or something similar.