Add cipher solutions with C++

[bhantsi]

What was changed?

Checklist

• [x] Added description of the change.
• [x] I acknowledge that all my contributions will be made under the project's license.

Program Request

• [x] Added file name matches File name guidelines mentioned in Contributing guidelines
• [x] Updated documentation OR created an issue for someone else to update the documentation.

Documentation Update

• [x] Documenation matches format mentioned in Contributing guidelines

Notes: These solutions use Caesar Cipher Algorithm to encrypt/decrypt plain text. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter with a fixed number of positions down the alphabet.