Add command nf-core subworkflows lint

[mirpedrol]

Close #1887

Implement nf-core subworkflows lint command

• implement command
• add pytests
• add lint tests
  • main.nf
  • meta.yml
  • changes compared to nf-core/modules repo
  • subworkflow tests
  • TODOs
  • version
• Write documentation

PR checklist

• This comment contains a description of changes (with reason)
• CHANGELOG.md is updated
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

[codecov]

Codecov Report

Merging #2379 (c4071f6) into dev (5a6d2b0) will decrease coverage by 1.96%.
Report is 2 commits behind head on dev.
The diff coverage is 44.75%.

@@            Coverage Diff             @@
##              dev    #2379      +/-   ##
==========================================
- Coverage   73.09%   71.14%   -1.96%     
==========================================
  Files          79       87       +8     
  Lines        9026     9395     +369     
==========================================
+ Hits         6598     6684      +86     
- Misses       2428     2711     +283     

Files Changed	Coverage Δ
nf_core/components/components_utils.py	48.19% <ø> (ø)
nf_core/modules/lint/main_nf.py	68.28% <ø> (ø)
nf_core/modules/lint/meta_yml.py	60.00% <ø> (ø)
nf_core/subworkflows/lint/main_nf.py	9.70% <9.70%> (ø)
nf_core/subworkflows/lint/meta_yml.py	11.53% <11.53%> (ø)
nf_core/subworkflows/lint/subworkflow_tests.py	14.58% <14.58%> (ø)
nf_core/subworkflows/lint/__init__.py	28.37% <28.37%> (ø)
nf_core/subworkflows/lint/subworkflow_todos.py	28.57% <28.57%> (ø)
nf_core/subworkflows/lint/subworkflow_changes.py	30.00% <30.00%> (ø)
nf_core/subworkflows/lint/subworkflow_version.py	30.43% <30.43%> (ø)
... and 18 more