Replace secp256k1-py lib

[HooriRn]

Hello everyone,

This wrapper should use a better library instead of secp256k1-py because it depended on the native secp256k1, which its installation is hard for some devs (most likely in windows and macOS). So I would recommend this to be replaced with other libs that support secp256k1 too, like electrumsv-secp256k1 or cryptography