Update Docker image

[ClaudiaComito]

• in docker/Docker.source, update pytorch image, create image
• update Package on landing page https://github.com/helmholtz-analytics/heat/pkgs/container/heat
• create separate Docker files for CUDA / ROCm (see existing CI https://codebase.helmholtz.cloud/helmholtz-analytics/ci/-/pipelines)
• update "singularity" docs (now Apptainer?)
• update docker/README.md
• Check if docker image runs on juwels-booster (If yes, with GPUs?)

[github-actions]

Branch features/1716-Update_Docker_image created!

[github-actions]

This issue is stale because it has been open for 60 days with no activity.