docs(readme): update root README to include HashMap project details

Author: singharyan006

README.md

@@ -1,23 +1,29 @@
-# 🧠  Algorithm Practice: Merge Sort, Fibonacci & Linked List
+# 🧠 Algorithm Practice: Recursion, Sorting, Linked List & HashMap
 
-This project contains simple yet fundamental algorithm implementations done as part of [The Odin Project](https://www.theodinproject.com/) curriculum. The focus is on recursive thinking and solving problems like the Fibonacci sequence, Merge Sort and Linked Lists from scratch using JavaScript.
+This project contains fundamental algorithm and data structure implementations, done as part of [The Odin Project](https://www.theodinproject.com/) curriculum.
+
+It focuses on **recursive thinking**, **sorting**, **linked lists**, and now also includes a complete custom-built **hash map** with resizing and collision handling.
 
 ---
 
 ## 📂 Files
 ```
-algo-practice
-  ├── recursion/
-  │    ├── iterative.js
-  │    └── recursive.js
-  ├── merge-sort/
-  │    └── mergeSort.js
-  ├── linked-list/
-  │    ├── Node.js
-  │    ├── LinkedList.js
-  │    ├── test.js
-  │    └── README.md
-  └── README.md
+algo-practice/
+├── recursion/
+│ ├── iterative.js
+│ └── recursive.js
+├── merge-sort/
+│ └── mergeSort.js
+├── linked-list/
+│ ├── Node.js
+│ ├── LinkedList.js
+│ ├── test.js
+│ └── README.md
+├── hashmap/
+│ ├── hashMap.js
+│ ├── test.js
+│ └── README.md
+└── README.md
 
 ```
 
@@ -34,6 +40,14 @@ algo-practice
 - LinkedList.js → Contains core linked list methods like:
   - `append()`, `prepend()`, `size()`, `at()`, `pop()`, `find()`, `contains()`, `toString()`
 - test.js → Sample test cases to validate the implementation
+
+### 🔐 `hashmap/`
+- Custom `HashMap` class with:
+  - Chained collision handling
+  - Resizing logic when load factor exceeds 0.75
+  - Methods like `set`, `get`, `has`, `remove`, `clear`, `keys`, `values`, `entries`
+- Notes + test cases included  
+➡️ [View detailed HashMap README →](./hashmap/README.md)
 ---
 
 ## 🚀 Sample Inputs & Outputs
@@ -59,14 +73,12 @@ mergeSort([105, 79, 100, 110]);
 ---
 
 ## 🧩 What I Learned
-- The difference between iterative and recursive thinking.
-- How to break problems down using base cases and divide & conquer logic.
-- The concept of mergeSort and how beautifully are these algorithms are directly associated with our real lives.
-- How recursion builds up the solution from the ground.
-- The importance of clean code, small reusable functions, and test-driven thinking.
-- The fundamentals of linked lists — how they work under the hood and how to implement one from scratch without built-in data structures.
-
 
+- The difference between iterative vs recursive solutions.
+- How to build data structures from scratch — LinkedList and HashMap.
+- Handling collisions and resizing logic in hash-based storage.
+- The importance of clear, testable, modular code.
+- How lower-level data structures power high-level abstractions.
 
 ---