Update README.rst: archived project

README.rst

@@ -4,6 +4,12 @@
    Contact Matgenix for commercial usage.
    See LICENSE file for details.
 
+.. warning::
+    The pysisso package has been archived. There was not much attraction from users anymore and no time to maintain. Also the new SISSO++ package, reimplemented in C++ and with python
+    bindings is likely to be more efficient and used. More information here: https://sissopp_developers.gitlab.io/sissopp/#
+
+    If you still have a need and would like support from us to revive the pysisso package, don't hesitate to contact us at info@matgenix.com.
+
 Python interface to the SISSO (Sure Independence Screening and Sparsifying Operator) method.
 ============================================================================================
 
@@ -31,4 +37,4 @@ Copyright
 Copyright (c) 2020, Matgenix SRL, All rights reserved.
 Distributed open source for academic and non-profit users.
 Contact Matgenix for commercial usage.
-See LICENSE file for details.
+See LICENSE file for details.