Add kmeans module

[AlexVCaron]

Added the KMeans module in modules/local/kmeans. I also created a main.nf pipeline file, for the only purpose of testing the KMeans module for now, and a nextflow.config for its configuration. I've done no documentation on the module, but if you know nf-neuro and understand task.ext, you'll be okay.

In addition :

• .gitignore file to ignore common nextflow run files
• Dockerfile with the beginning of a definition on top of scilus/scilus:latest (for now)
• devcontainer using the aformentioned Dockerfile. So we can test in an environment as close to the challenge as possible