Linked list

[anirudh-satheesh]

What does this PR do? This PR adds a new folder named "linked list" under the Hacktoberfest contribution. It includes implementations for three different types of linked lists:

x) Singly Linked List x) Doubly Linked List x) Circular Linked List

Type of change New feature (non-breaking change which adds functionality)

To verify the functionality of the linked list implementations:

*Run the provided code for all three types of linked lists and check the output for correct behavior (insertion, deletion, traversal, etc.). *Ensure there are no errors or warnings during compilation or execution. Mandatory Tasks [x] Self-review the code to ensure it follows the required style and standards for the repository. [ ] Add relevant comments and documentation if necessary.