Add LEARN.md to guide new contributors with tech stack and GSSoC info

LEARN.md

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+# 📘 LEARN.md
+
+Welcome to the KnockOutZone Learning Guide!
+
+This document is designed to help new contributors get up to speed with the technologies used in this full-stack web application and start contributing effectively.
+
+---
+
+## 🧰 Overview of Technologies Used
+
+| Layer     | Technology                     |
+|-----------|--------------------------------|
+| Frontend  | React, TailwindCSS             |
+| Backend   | Java (Spring Boot)             |
+| Database  | PostgreSQL                     |
+| Auth      | JWT (JSON Web Tokens)          |
+| Realtime  | Socket.IO / REST Polling       |
+| Deployment| Vercel (Frontend), Render / Railway (Backend) |
+
+---
+
+## 📚 Learning Resources
+
+### React (Frontend)
+- [React Official Docs](https://reactjs.org/docs/getting-started.html)
+- [React Crash Course (YouTube)](https://www.youtube.com/watch?v=w7ejDZ8SWv8)
+- [TailwindCSS Docs](https://tailwindcss.com/docs)
+
+### Java & Spring Boot (Backend)
+- [Spring Boot Beginner Guide](https://spring.io/guides/gs/spring-boot/)
+- [Java Brains - Spring Boot Playlist](https://www.youtube.com/playlist?list=PLqq-6Pq4lTTZSKAFG6aCDVDP86Qx4lNas)
+
+### PostgreSQL (Database)
+- [PostgreSQL Tutorial](https://www.postgresqltutorial.com/)
+- [SQL Basics](https://www.w3schools.com/sql/)
+
+### Authentication - JWT
+- [JWT Intro](https://jwt.io/introduction)
+- [Spring Security + JWT Guide](https://www.baeldung.com/spring-security-oauth-jwt)
+
+### Real-Time Communication
+- [Socket.IO Documentation](https://socket.io/docs/)
+- [REST Polling Basics](https://dev.to/kiranrajvjd/rest-vs-websockets-vs-server-sent-events-1bfd)
+
+### Deployment
+- [Vercel Documentation](https://vercel.com/docs)
+- [Render Deployment Guide](https://render.com/docs/deploy-a-spring-boot-app)
+- [Railway Deployment](https://docs.railway.app/)
+
+---
+
+## 🧑‍💻 Tips for New Contributors
+
+- **Start small:** Begin with documentation, UI fixes, or refactoring tasks.
+- **Read `CONTRIBUTING.md`:** Understand how to set up and contribute.
+- **Understand the flow:** Explore how players register, how matches are scheduled, and how scores are updated.
+- **Ask questions:** Don't hesitate to ask maintainers or others in the Discord server.
+
+---
+
+## 🛠 Suggested First-Time Setup
+
+1. **Clone the repository**
+2. **Set up the backend** (Java + Spring Boot + PostgreSQL)
+3. **Run the frontend** (React + TailwindCSS)
+4. **Explore the app locally**
+5. **Pick an issue and start contributing!**
+
+---
+
+## 🐞 Troubleshooting
+
+Here are some common issues you might face while setting up or contributing, along with suggested solutions:
+
+### 1. **Backend Not Starting (Java/Spring Boot Errors)**
+- **Solution:** Ensure you have Java 17 or higher installed.
+- Check if your PostgreSQL database is running and the credentials in `application.properties` are correct.
+
+### 2. **Database Connection Failed**
+- **Solution:** 
+  - Make sure PostgreSQL is installed and the DB service is running.
+  - Double-check your DB name, username, and password in the config files.
+  - Check for any firewall or port blockages (default is port `5432`).
+
+### 3. **Frontend Crashes or Doesn’t Load**
+- **Solution:** 
+  - Run `npm install` or `yarn` in the frontend directory to install dependencies.
+  - Use `npm run dev` or `npm start` (depending on setup).
+  - Ensure the backend server is running if the frontend depends on API calls.
+
+### 4. **CORS Errors in Browser Console**
+- **Solution:** 
+  - Add CORS configurations in the Spring Boot backend (usually in a WebConfig file or Controller).
+  - You can temporarily disable CORS in development using browser extensions (not recommended for production).
+
+### 5. **Real-time Features Not Working (Socket.IO)**
+- **Solution:**
+  - Check if the backend server has Socket.IO setup and is running.
+  - Confirm that both frontend and backend are using the correct socket URL and port.
+
+### 6. **Build/Deployment Errors (Vercel, Render, Railway)**
+- **Solution:**
+  - Review build logs provided by the platform.
+  - For frontend (Vercel), ensure the build command and output directory are correctly set in project settings.
+  - For backend (Render/Railway), ensure environment variables are correctly configured.
+
+---
+
+## 📎 Additional Documentation
+
+- [`README.md`](./README.md) – Project Overview
+- [`CONTRIBUTING.md`](./CONTRIBUTING.md) – Contribution Guide
+- [`LICENSE`](./LICENSE) – License Info
+
+---
+
+## 🌟 GSSoC Notes
+
+If you're contributing as part of **GSSoC'25**, here’s how you can make the most out of it:
+
+### 🏁 Getting Started
+- Look for issues labeled with `gssoc` or `good first issue`.
+- If you find an unlabeled issue you want to work on, **ask for it to be assigned** in the comments.
+- Follow the `CONTRIBUTING.md` file to set up your environment and make your first PR.
+
+### 🛠️ Contribution Tips
+- Always comment on an issue before starting work to avoid duplication.
+- Make small, focused PRs with meaningful commit messages.
+- Ask questions in the Discord server if you're stuck — mentors and maintainers are here to help!
+
+### 💡 Ideas for Contributions
+- Improve project documentation (`README.md`, `LEARN.md`, `CONTRIBUTING.md`)
+- Add frontend UI enhancements
+- Fix backend bugs or refactor Java/Spring Boot code
+- Help test features and report issues
+- Write or improve error handling, validations, or accessibility
+
+We’re excited to have you on board. Good luck and happy contributing! 💻🚀 
+