nixos/release-notes: add saunafs under "New modules" sections

Author: markuskowa

nixos/doc/manual/release-notes/rl-2411.section.md

@@ -175,6 +175,8 @@
 
 - [Immich](https://github.com/immich-app/immich), a self-hosted photo and video backup solution. Available as [services.immich](#opt-services.immich.enable).
 
+- [saunafs](https://saunafs.com) Distributed POSIX file system. Available as [services.saunafs](options.html#opt-services.saunafs).
+
 - [obs-studio](https://obsproject.com/), Free and open source software for video recording and live streaming. Available as [programs.obs-studio.enable](#opt-programs.obs-studio.enable).
 
 - [Veilid](https://veilid.com), a headless server that enables privacy-focused data sharing and messaging on a peer-to-peer network. Available as [services.veilid](#opt-services.veilid.enable).