[MRG + 1] DOC Add sklearn-porter to related projects (scikit-learn#7945)

* DOC Add sklearn-porter to related projects

* DOC Replace 'low-level' wording

Author: nok

doc/related_projects.rst

@@ -44,6 +44,9 @@ enhance the functionality of scikit-learn's estimators.
   into PMML with the help of `JPMML-SkLearn <https://github.com/jpmml/jpmml-sklearn>`_
   library.
 
+- `sklearn-porter <https://github.com/nok/sklearn-porter>`_
+  Transpile trained scikit-learn models to C, Java, Javascript and others.
+
 Other estimators and tasks
 --------------------------