[no version bump yet] better and safer stdlib impl

only transformed configs/with_string so far,
but other configs/* should follow soon.
also, this will help with implementing
new stdlib functions in the future.

mers_lib/src/program/configs/mod.rs

@@ -7,6 +7,7 @@ use crate::{
     program::run::CheckInfo,
 };
 
+pub mod gen;
 pub mod util;
 pub mod with_base;
 pub mod with_command_running;