enhance README with detailed setup and add .env.example

[iamkrshivam]

Summary

This PR improves the project documentation and configuration setup:

• Enhanced README.md – Made it more detailed, structured, and visually attractive. Added badges, a clear table of contents, step‑by‑step installation with Yarn, environment variable usage, and a troubleshooting section.
• Added .env.example – Provides a template for all required environment variables (e.g., PORT, MONGO_URL, SESSION_SECRET), making it easier for new users to configure the application.

Changes

• readme.md – Restructured, added badges, clarified installation steps (Yarn), included an “Environment Variables” section referencing .env.example, and improved formatting.
• .env.example – New file with placeholder values and comments for every configuration variable used by the app.

Testing

• Followed the updated README instructions on a fresh clone.
• Copied .env.example to .env, filled in local values.
• Ran npm install and gulp – the application started successfully.
• Verified that the README accurately reflects the current setup process (Yarn, Bower via postinstall, MongoDB seeding).

Related Issues

Closes #32 (if that issue is about outdated setup instructions – adjust as needed).
Helps with contributor onboarding and environment configuration.