Fixes harry-s-grewal#16

Dockerizes the project and sets up automated Docker image publishing to GitHub Container Registry.

* **Dockerfile**: Adds a `Dockerfile` to build the Docker image using `python:3.9-slim` as the base image, installs dependencies, copies application code, and sets the entry point to `python`.
* **README.md**: Updates the `README.md` with instructions on how to build and run the Docker image.
* **GitHub Actions Workflow**: Adds a GitHub Actions workflow file (`.github/workflows/docker-publish.yml`) to build and publish the Docker image to `ghcr.io` on push to the `main` branch.
* **Dependabot Configuration**: Adds a Dependabot configuration file (`.github/dependabot.yml`) to enable weekly updates for `pip` dependencies, GitHub Actions, and Docker images.

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