Mention other, preferred, packages in docs

[FBruzzesi]

QuantileRegressor made it into scikit-learn some time ago already.

As in the future other features could lose the experimental status and be incorporated as well (I am looking at you TunedThresholdClassifier) should we plan to deprecate them in future versions of scikit-lego?

[koaning]

I've been wondering about this myself as well. The sklearn spline transformer now also does the repeating basis function trick ... so technically we won't need to have it around here.

Then again ... I also don't mind to brag. I think it was hosted on the lego side first, so maybe a message that just says "we're keeping it around for historical reasons because sklearn has support for it now" is fine? I don't mind to communicate that sklego is a testing ground for experimental ideas.

[FBruzzesi]

It seems fair and square! I will add a couple of info notes in the docstrings just to let users know.

[koaning]

I'll write a list of items that might fall under this category, feel free to add.

• Some of our fairness docs should point to fairlearn
• The quantile docs should point to sklearn
• The repeating basis trick should point to the spline transformer in sklearn.