add: Contribution guide

CONTRIBUTING.md

@@ -0,0 +1,43 @@
+### Wanna Contribute 🤔??
+
+- #### 🍴 Create a Fork of this repo to your GitHub Account
+
+  ![Alt text](./public/demo/contribute.png)
+
+- #### 🧑🏽‍💻 Clone the Your Repo Locally
+
+  first open your CLI and clone the repo locally. But don't forget put your github username in **username**
+
+  ```bash
+  git clone https://github.com/username/alfa-leetcode-api.git
+  ```
+
+- #### 👋🏽 Go to the project folder
+
+  ```bash
+  cd alfa-leetcode-api
+  ```
+
+- #### 🚀 Install Require modules
+
+  ```bash
+  npm install
+  ```
+
+- #### 🏃🏽‍♂️Run Project Locally
+
+  ```bash
+  npm start
+  ```
+
+- #### 💡 Make Changes & Pull Requests
+
+  Make changes as require and push it to your GitHub with proper **commit message**. From their Create a **PR(Pull Request)** and submit it.
+
+- #### 📌 Additional Tip
+
+  Try to make a new branch relevant to your work. For example - `fix:xyz-issue`
+
+  📝Note - It's not Necessary for contribution but it will help me to marge it.
+
+#