CD - Add GitHub Action to push Docker image to Docker Hub

[Juansecu]

Add a GitHub Action to automatically push an official Docker image of OpenFusion server to Docker Hub every time a new release is published.

The following secrets are necessary:

• DOCKERHUB_TOKEN - A Docker Hub token with write permissions
• DOCKERHUB_USERNAME - The user of Docker Hub who will be pushing the Docker image
• DOCKERHUB_REPOSITORY - The Docker Hub repository where the Docker image will be pushed to