Add README.md for gepetto mindmap.

pictures/mindmaps/README.md

+# Mindmaps
+
+This directory collect mindmaps useful to better understand the organization in the Gepetto Group.
+
+## Gepetto
+This map gives an overview of the various scientific subjects tackled in the group.
+It can be edited using Inkscape. Last edition Inkscape 1.1.1 on mac Big Sur 11.6
+
+
+