Add warning re. the need for disk encryption

This MR adds a warning to encourage people to encrypt their devices' local storage.

With the new security subsidiary rules, encryption of laptops/PCs/etc. is mandatory. We should encourage people to do this at install time, as re-installing after the fact is a major hassle. See also https://home.cern/news/news/computing/computer-security-dont-let-your-data-walk-away

Happy to adjust the wording.

docs/almalinux/alma8/stepbystep.md

@@ -37,6 +37,10 @@ You will need to provide input for the items marked in red, 'Keyboard', 'Time &
 
 Select the device to be used for the installation:
 
+!!! warning
+    As of 2025, all CERN-owned "endpoints" (e.g. laptops and office PCs) [must have their local storage encrypted](https://security.web.cern.ch/rules/en/ept.shtml). If this applies to you, make sure to check the "Encrypt my data" box.
+    This is strongly recommended for personal devices as well.
+
 ![Select Device](/almalinux/alma8/installshots/partitioning.png "Select Device")
 
 If selected device has been already used for previous version of operating system use 'Reclaim space':