Crest, Shape and Impulse factor

[vutle]

Could we add the crest factor inside the feature set please.

[nils-braun]

Sure! Thanks for the suggestion.
Would you like to open a PR for these features? We welcome any contribution!
Have a look into the docu here and [here]https://tsfresh.readthedocs.io/en/latest/text/how_to_contribute.html] if this is your first-time contribution to tsfresh.

Would love to see this!