Split steps create lint wf

[ewels]

• Split up CI commands into separate steps for create-lint-wf to make it easier to read
• Added automated PR comments for markdown + Python code linting CI

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 #941 (c9a3b11) into dev (1c0291e) will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##              dev     #941      +/-   ##
==========================================
+ Coverage   69.56%   69.59%   +0.02%     
==========================================
  Files          34       34              
  Lines        4173     4173              
==========================================
+ Hits         2903     2904       +1     
+ Misses       1270     1269       -1     

Impacted Files	Coverage Δ
nf_core/__main__.py	61.58% <0.00%> (+0.31%)	⬆️

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[KevinMenden]

Really like those comments about Black 👍

[ewels]

Would be good to test them on dev before release to be sure that I haven't messed up the formatting etc - quite easy to do.

[ewels]

..to clarify, I mostly mean that because if they work I would like to add them to the pipeline template too 👍🏻