Add the ability to hash arrays [Feature]

[matthewdgreen]

🚀 Feature

Currently the documentation indicates that we can hash structs using hash functions like Poseidon. But this capability does not work for other static structures like arrays. Can Leo be made to treat arrays as though they are structs, so we can then hash them?

Motivation

There are many applications where the ability to hash arrays is useful, just as the ability to hash arrays is useful.

Implementation

I'm hopeful this is as simple as making a type cast in the high level language compiler.