docs: end of life

README.md

 # simplesamlphp-module-campusmultiauth
 
+![maintenance status: end of life](https://img.shields.io/maintenance/end%20of%20life/2024)
+
+This project has reached end of life, which means no new features will be added. Security patches and important bug fixes ended in May 2024. Check out [Apereo CAS](https://apereo.github.io/cas/) and [ProxyIdP GUI](https://gitlab.ics.muni.cz/perun/perun-proxyidp/proxyidp-gui) instead.
+
+## Description
+
 Thanks to this module, you can use a saml:SP authentication source together with another authentication source providing basic auth (discovery service and login form are displayed on a single page).
 
 ## Theme configuration