Add Unit Test for - LRU Cache

[TheSTL]

🤡 What is required?

The algorithm is here : LRU-Cache

• Follow the ESLint rules strictly
• Follow the filename and folder structure strictly
• Since the Contribution Guide is not ready yet, go through the codebase pattern and add tests accordingly

Thank You!

[luhego]

I created a pull request for this issue:
#77

[TheSTL]

I'm closing this issue because PR is merged. [#77 ]