Add SPIS (#3620)

README.md

@@ -1576,6 +1576,7 @@ A [gallery](https://en.wikipedia.org/wiki/Gallery_Software) is software that hel
 - [Piwigo](https://piwigo.org/) - Photo gallery software for the web, built by an active community of users and developers. ([Source Code](https://github.com/Piwigo/Piwigo)) `GPL-2.0` `PHP`
 - [Quru Image Server](https://quruimageserver.com/) - High performance dynamically resizing image server offering directory based access control cropping, rotation, color management and other tools. ([Demo](https://quruimageserver.com), [Source Code](https://github.com/quru/qis)) `AGPL-3.0` `Python`
 - [sigal](https://github.com/saimn/sigal) - Yet another simple static gallery generator. `MIT` `Python`
+- [SPIS](https://github.com/gbbirkisson/spis) - A simple, lightweight and fast media server with decent mobile support. `GPL-3.0` `Rust`
 - [This week in past](https://github.com/RouHim/this-week-in-past) - Aggregates images taken this week, from previous years and presents them on a web page with a simple slideshow. ([Demo](http://152.70.175.46:80)) `MIT` `Docker/Rust`
 - [Thumbor](http://thumbor.org/) - A smart imaging service and enables on-demand cropping, resizing, applying filters and optimizing images. ([Source Code](https://github.com/thumbor/thumbor)) `MIT` `Python/Docker`
 - [UberGallery](https://www.ubergallery.net) - UberGallery is an easy to use, simple to manage, web photo gallery. UberGallery does not require a database and supports JPEG, GIF and PNG file types. Simply upload your images and UberGallery will automatically generate thumbnails and output HTML. ([Source Code](https://github.com/UberGallery/UberGallery)) `MIT` `PHP`