[feat]: Enums added with test function also added immutable and const…

[Smr0303]

👨‍💻 Changes proposed

1. Added a constant variable with a random name to show how to declare constants
2. Added immutable variable to show how to declare immutable variables in constructor
3. Added Enums
4. Added demo functions for Enums to describe the functionalities of Enum

✔️ Check List (Check all the applicable boxes)

• [✔️ ] My code follows the code style of this project.
• [ ✔️] This PR does not contain plagiarized content.
• [✔️ ] The title of my pull request is a short description of the requested changes.

[github-actions]

Our team will soon review your PR. Thanks @Smr0303 :)