Added libre-studio to the Utilities list (#90)

Added a reference to libre-studio under the Utilities list, a management layer for maplibre martin

README.md

@@ -261,6 +261,7 @@ are designated with a ✅, and hosted projects with a 💙.
 - [MapBlockly](https://mapblockly.github.io/) - MapBlockly is a simple and fun way to learn and build Map with Blockly using MapLibre.
 - [MapInventor](https://mapinventor.github.io/) - MapInventor is the visual language built on top of MapBlockly.
 - [Ultra](https://overpass-ultra.us/) - A web-based IDE for making maps with MapLibre, supporting a variety of query & file types such as Overpass, ohsome, GeoJSON, KML, and more. [docs](https://overpass-ultra.us/docs)
+- [Libre-studio](https://github.com/BleenIT/libre-studio) - A web-based management layer for Maplibre Martin, allowing the management of map sources, sprites and font glyphs, for ready-to-use custom maps.
 
 ## Users