Edits and documentation for successful Kubernetes execution of workflow

[pinin4fjords]

Hi Kaur and Nurlan,

This is not so much of a request for changes as a note of what is required to run this workflow on the Kubernetes, specifically an Embassy-hosted k8s at the EBI.

• Functions in the config are a known issue with nf-core workflows and k8s, so we need to strip out check_max()
• The 'container' declaration must come under 'process', not 'params'
• There seems to be a kuberun issue with memory units we must work around (see https://github.com/nextflow-io/nextflow/issues/1372)
• $USER is not available to the containers, so I've reset that back to the workflow parameter.

I've also added a doc describing the process.