Fix #270: Added function docstrings and cleaned up cipher logic

[vivek65666]

Description

Added comprehensive Python docstrings to class and function definitions, fixed confusing variable naming, and optimized dictionary lookups in the Caesar Cipher project.

Fixes #270

• Issue_no: 270
• Not applicable

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Documentation Update

Project

• Your Project Name: Caesar_Cipher

• Short Description: Added missing function docstrings, fixed method logic, and updated string prompt messages for improved code clarity.

Checklist:

• I have named my files and folder, according to this project's guidelines.
• My code follows the style guidelines of this project.
• I have commented on my code, particularly in hard-to-understand areas.
• I have created a helpful and easy to understand README.md, according to the given README_TEMPLATE.
• My changes do not produce any warnings.

Closes #270