nixos/doc/rl-2505: Mention Pantheon 8

nixos/doc/manual/release-notes/rl-2505.section.md

@@ -319,6 +319,10 @@
   - Following [changes in Mint 22](https://github.com/linuxmint/mintupgrade/commit/f239cde908288b8c250f938e7311c7ffbc16bd59) we are no longer overriding Qt application styles. You can still restore the previous default with `qt.style = "gtk2"` and `qt.platformTheme = "gtk2"`.
   - Following [changes in Mint 20](https://github.com/linuxmint/mintupgrade-legacy/commit/ce15d946ed9a8cb8444abd25088edd824bfb18f6) we are replacing xplayer with celluloid since xplayer is no longer maintained.
 
+- Pantheon has been updated to 8, please check the [upstream announcement](https://blog.elementary.io/os-8-available-now/) for more details.
+  - Same as elementary OS, the X11 session is named "Classic Session" and the Wayland session is named "Secure Session".
+  - The dock has been rewritten, you need to manually migrate the dock items on update. You can check `~/.config/plank/dock1/launchers/` for your previous settings.
+
 - Xfce has been updated to 4.20, please check the [upstream feature tour](https://www.xfce.org/about/tour420) for more details.
   - Wayland session is still [experimental](https://wiki.xfce.org/releng/wayland_roadmap) and requires opt-in using `enableWaylandSession` option.
   - Overriding Wayland compositor is possible using `enableWaylandSession` option, but you might need to take care [`xfce4-session`](https://gitlab.xfce.org/xfce/xfce4-session/-/merge_requests/49), [`dbus-update-activation-environment`](https://github.com/labwc/labwc/blob/eaf11face68ee1f1bcc7ce1498304ca8c108c8ba/src/config/session.c#L234) and [`systemctl --user import-environment`](https://github.com/labwc/labwc/blob/eaf11face68ee1f1bcc7ce1498304ca8c108c8ba/src/config/session.c#L239) on startup.