Add Mailsail OS

Author: JWolvers

README.md

@@ -65,6 +65,7 @@ The complete collection of (consumer) Raspberry Pi models consist of:
 - [KonstaKANG](https://konstakang.com/devices/rpi4/) - Unofficial LineageOS and AOSP builds for Raspberry Pi. ![Supports Raspberry Pi 3](/media/badges/rpi-3.png)
 - [Lakka](http://lakka.tv) - Retro-gaming on the Raspberry Pi built entirely on RetroArch.
 - [LibreELEC](https://libreelec.tv/) - Just enough OS for Kodi
+- [Mainsail OS](https://github.com/mainsail-crew/MainsailOS) - A distribution for 3D Printers that includes everything to get started with Klipper Firmware and Mainsail.
 - [Manjaro](https://manjaro.org/download/) - Friendly, open-source Linux distribution for Raspberry Pi.
 - [Minibian](https://minibianpi.wordpress.com/) - Minimal Raspbian (lighter than Jessie Lite).
 - [MoodleBox](https://moodlebox.net/) - The MoodleBox provides a Moodle learning management system on Raspberry Pi. ![Supports Raspberry Pi 3](/media/badges/rpi-3.png)