Remove missing file + Add LRU Cache implementation

[luckyb13]

Pull Request: Remove missing file and add LRU Cache implementation

Changes Made

• Removed outdated reference to file "a" which was previously moved and no longer exists.
• Added new file "lru-cache.js" implementing a fully functional Least Recently Used (LRU) cache.

LRU Cache Implementation Summary

• Uses JavaScript Map to maintain insertion order for tracking usage.
• Provides O(1) get and put operations.
• Automatically evicts least-recently-used entry when capacity is reached.
• Includes utility functions: has, delete, clear, size.
• Includes validation: capacity must be an integer greater than or equal to 1.
• Includes documentation comments for clarity.

Usage Example

import { LRUCache } from "./lru-cache.js";

const cache = new LRUCache(2);
cache.put("a", 1);
cache.put("b", 2);
cache.get("a"); // a becomes most recently used
cache.put("c", 3); // evicts key "b"

console.log(cache.get("b")); // -1
console.log(cache.get("a")); // 1
console.log(cache.get("c")); // 3

This contribution adds real functionality and improves repository quality. Please add the label:

hacktoberfest-accepted

Thank you.