Add Dockerfile with Graphviz binary support

[matiasAS]

This PR adds a Dockerfile to run PyFRC2G in a container with the Graphviz dot
binary installed, avoiding host system dependencies.

No code changes included.

[matiasAS]

@olivierb46 adding a usage example for the Docker image in case it is useful.

As a usage example, the container can be executed like this:

docker run --rm \
  -e PFS_BASE_URL=<PFS_BASE_URL> \
  -e PFS_TOKEN=<PFS_TOKEN> \
  -v $(pwd)/results:/app/results \
  pyfrc2g

This runs PyFRC2G inside the container without requiring Graphviz or other system dependencies to be installed on the host.

The results directory will be created on the host if it does not already exist, and all generated output will be written there.

Environment variables are passed at runtime to avoid hardcoding sensitive credentials.

[olivierb46]

hi @matiasAS ,

Thank you very much for your contribution. I tested it yesterday (without environment variables for now) and have a few comments:

• You need to use the requirements.txt file to install the Python libraries.
• The Docker container should not run as root by default. It's Ok if we use this option --user $(id -u):$(id -g) but I think it needs to be more secure.
• -v $(pwd)/results:/app/results causes a permission error with the --user option, or it does not produce any files without this option. I had to specify -v $(pwd):/app instead.

Thanks again ;)