Semaphore example package

This is basically a wrapper around/copy of https://github.com/worldcoin/semaphore-rs to illustrate how e.g. RLN package can be structured like.

Goal is also to provide a basic FFI around protocol.rs, which is currently not in scope for that project.

See that project for more information.

Build and Test

To build and test, run the following commands within the module folder

cargo make build
cargo make test