Containerize the applocation for better developer support

## Summary
beacon-backend is a nodejs application that uses mongodb for databasing and redis for pub-sub architecture. Containerizing this application would greatly help the developers to setup and work with the repository. This will speed up the development and testing processes too.

- Cotainerizing the application using docker and docker compose
- setting up the database instances in docker compose file for easy database spin up
- modifying the `.env.example` and insert all the values as per the docker container

## Implementation
- Create a Dockerfile for the NodeJS application
- Set up a docker-compose.yml file that includes:
The application service
MongoDB service with persistent volume
Redis service
- Update the .env.example file with appropriate Docker network references
- Add documentation for local development with Docker

I would like to work on this issue. Please assign me @aadibajpai .