Update README.md

Author: simongravelle

README.md

@@ -3,6 +3,8 @@
 This is the repository of the [LAMMPS tutorials](https://lammpstutorials.github.io/)
 webpage. All the LAMMPS input scripts and data files can be found in a separate repository named [lammpstutorials-inputs](https://github.com/lammpstutorials/lammpstutorials-inputs).
 
+The tutorials are compatible with the 2Aug2023 stable release of LAMMPS.
+
 ## About LAMMPS tutorials
 
 The LAMMPStutorials website is made of seven tutorials that are ordered by increasing difficulty.