impl hash committed instance gadget (#17) (#31)

together with the native impl compatible with the gadget one

src/folding/circuits/mod.rs

@@ -3,6 +3,7 @@ use ark_ec::CurveGroup;
 use ark_ff::Field;
 
 pub mod cyclefold;
+pub mod nonnative;
 
 // CF represents the constraints field
 pub type CF<C> = <<C as CurveGroup>::BaseField as Field>::BasePrimeField;