Adding substitution cipher in cryptography

This is a(n):

• New algorithm
• Update to an existing algorithm
• Error
• Proposal to the Repository

Details:

In cryptography, a substitution cipher is a method of encrypting in which units of plaintext are replaced with the ciphertext, in a defined manner, with the help of a key;

@AdiChat Could you please assign me this issue with Hacktoberfest tag so that can I can start contributing to this repo.

Thankyou