This commit introduces the implementation of Schnorr signatures following BIP-340, including the `SchnorrSign` and `SchnorrVerify` functions. It also adds comprehensive tests to validate the signing and verification processes, ensuring correct functionality with both standard and auxiliary randomness. The tests cover various scenarios, including signature generation, verification, and edge cases, enhancing the robustness of the secp256k1 implementation. Additionally, new files for Schnorr signature operations and tests have been created, contributing to the overall cryptographic capabilities of the library.
