Added 206_Reverse_Linked_list.cpp code

[Tushar161101]

Description

The idea is to reach the last node of the linked list using recursion then start reversing the linked list.

Put check marks:

Have you made changes in README file ?

• [Done] Added problem & solution under correct topic.
• [Done] Specified Space & Time complexity.
• [Done] Specified difficulty level, tag & Note(if any).

How Has This Been Tested?

On LeetCode PlatForm

Make sure all below guidelines are followed else PR will get Reject:

• [Done] My code follows the style guidelines of this project
• [Done] I have performed a self-review of my own code
• [Done] I have commented my code so that it is easy to understand
• [Done] I have made corresponding changes to the documentation
• [Done] My changes generate no new warnings
• [Done] Any dependent changes have been merged and published in downstream modules

[welcome[bot]]

I can tell this is your first pull request! Thank you I'm so honored. :tada::tada::tada: I'll take a look at it ASAP!