Exposing apca's version of num_decimal

[AshrafIbrahim03]

I ran into this issue while making an application so I figured I'd just make this PR. When using apca it's been a pain trying to use the num_decimal crate along with it. I figured that just exporting it in apca would help because someone using this crate doesn't have to dig through the code to get the specific version number for compatibility.

[CAReyes]

I too would like this to be added. I would also like the option to use rust_decimal since it seems to be more widely used but that would require a large rework of this crate.