nixos/doc: add release note for sftpgo

nixos/doc/manual/release-notes/rl-2305.section.md

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 - [atuin](https://github.com/ellie/atuin), a sync server for shell history. Available as [services.atuin](#opt-services.atuin.enable).
 
+- [SFTPGo](https://github.com/drakkan/sftpgo), a fully featured and highly configurable SFTP server with optional HTTP/S, FTP/S and WebDAV support. Available as [services.sftpgo](options.html#opt-services.sftpgo.enable).
+
 - [esphome](https://esphome.io), a dashboard to configure ESP8266/ESP32 devices for use with Home Automation systems. Available as [services.esphome](#opt-services.esphome.enable).
 
 - [networkd-dispatcher](https://gitlab.com/craftyguy/networkd-dispatcher), a dispatcher service for systemd-networkd connection status changes. Available as [services.networkd-dispatcher](#opt-services.networkd-dispatcher.enable).