Added ChaCha20 Cryptographic Algorithm Implementation

[Susmita331]

This PR introduces the implementation of the ChaCha20 cryptographic algorithm, a high-speed and secure stream cipher widely used for encryption. The implementation includes:

The ChaCha20 quarter-round function

• Key scheduling and initialization of the ChaCha state matrix
• The generation of keystream blocks for encryption/decryption
• Support for nonce and counter-based operations

This addition enhances the cryptographic capabilities of the project, ensuring efficient and secure encryption suitable for various applications.