32-bit and 64-bit compatibility testing

[fjarri]

Since the code of this library is intended to be run both on 32- (e.g. WASM) and 64-bit platforms, and needs to perform consistently on all of them, we need to test that behavior. There has already been an issue with the ZK proof challenges being generated differently on different bitness (see #45).

To test that, we need to somehow run the protocol sessions with different nodes using different bitness. How do we do that? Can we use the existing WASM bindings to simulate a 32-bit target?