Add new custom builtin functions

[mainrs]

Is it possible to add new custom builtins? I am in need of functions that perform some IO when called and return a value that can be used inside the configuration.

[Nadrieril]

It isn't unfortunately. I wanted to but it would have been a pretty complex API so I never got around to implementing it. The easiest would be to fork the repo and hard-code your funciton, but even then this codebase is a mess ><