Add tutorial on how to estimate a Cox Proportional Hazards Model in g…

…lum (#876)

* add tutorial

* first version

* add anchors and adjust format

* title case

* categoricals

* tiny changes

* even more cosmetics

* wording

* add lifelines optional dependency

* tiny wordings

* add lifelines to pixi lock

* even more tiny wordings

* add output for all cells

* clearer notation and small wordings

* some more words on data part

* update pixi lock

* add reference to penalized splines blog post

* Apply suggestions from code review

Co-authored-by: Martin Stancsics <[email protected]>

* suggestion & add conclusion

* add clarifying sentence

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Co-authored-by: Martin Stancsics <[email protected]>