Add password hashing functions with `scrypt`

I think it would be within the scope of this library to provide two functions `hashPassword` and `verifyPassword`.

These are already implemented in `better-auth` [here](https://github.com/better-auth/better-auth/blob/377ddf3054c8ca922c48ec943d2b87936e1f7836/packages/better-auth/src/crypto/password.ts) and I think it would make sense to extract them into this library.