Upgrade roadmap to newest versions of nf-core template

Feedback from peer-review:

[ ] Fix warning: WARN: Access to undefined parameter 'enable_conda' -- Initialise it to a default value eg. 'params.enable_conda = some_value'
[ ] Include input validation using the nf-validation plugin to replace SAMPLESHEET_CHECK: https://github.com/qbic-pipelines/root-tissue-analysis/blob/b8c687630405bd9b86a32da60fcaf217aa5e4492/modules/local/samplesheet_check.nf#L6
[ ] Update to the newest versions of the nf-core template (https://nf-co.re/docs/tutorials/nextflow_training/creating_with_nf-core)

qbic-pipelines / root-tissue-analysis