Fix: #42 Add Dockerfile and docker-compose for containerization

[MohakGupta2004]

This pull request introduces Docker support to the project, enabling easier setup and deployment of the application in a containerized environment. The changes include:

Dockerfile: A Dockerfile has been created to define the containerized environment for the Node.js application, including dependencies, environment variables, and build configurations.
docker-compose.yml: A docker-compose.yml file has been added to simplify the process of running multiple services (such as the Node.js app and MongoDB) in development.
Environment Variables: Default environment variables have been set up for local development, such as PORT, MONGO_URI, and JWT_SECRET. These can be easily overridden in .env files or the Docker Compose configuration.

Summary of Changes:

Added Dockerfile for Node.js application containerization.
Added docker-compose.yml for local development environment (with MongoDB service).
Updated .env example with relevant environment variables.
Exposed application port and MongoDB service through Docker Compose.