Recovery of wrappers for River and Scikit-learn

We are currently preparing to relocate most wrappers to separate GitHub repositories. Unfortunately, we removed the wrappers for River and Scikit-learn too early from the MLPro main project. Here's the recovery of both. We apologize for the inconvenience.

What's Changed

3rd Party Support / Wrappers

• Bug: Recovery of wrappers and howtos for River and Scikit-learn #913 by @detlefarend in #914

Full Changelog: v1.3.0...v1.3.1