S. Riette 21 Nov 2022: add the wiki link to README

README.md

@@ -3,3 +3,4 @@ PHYsique EXternalisée
 
 Documentation can be found in the [docs directory](./docs/PHYEX.md).
 
+Several presentations were done, the materials can be found on the [wiki](https://github.com/UMR-CNRM/PHYEX/wiki).