Add cognitive complexity metric

[priv-kweihmann]

https://pypi.org/project/cognitive-complexity/

and following

https://www.sonarsource.com/docs/CognitiveComplexity.pdf
https://docs.codeclimate.com/docs/cognitive-complexity

as the original approach is for function/blocks only, maybe a weighted metric taking loc into account would be nice

[ruimaranhao]

Are there any plans to deploy this metric soon?

[priv-kweihmann]

TBH, no - but patches are welcome - active development is more or less on hold at the moment