init practice file notebook for model selection and regularization

Practical_d.Rmd

+---
+# https://www.gnu.org/licenses/agpl-3.0.txt
+title: "Practice: Introduction to model selection and regularization"
+author: "Ghislain Durif, Laurent Modolo, Franck Picard"
+---
+
+<a rel="license" href="http://creativecommons.org/licenses/by-sa/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/l/by-sa/4.0/88x31.png" /></a><br />This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-sa/4.0/">Creative Commons Attribution-ShareAlike 4.0 International License</a>