Add a libre reimplementation of a Unity3D plugin

This plugin lets users configure the resolution, quality and controls
before starting the game. The proprietary original uses gtk2 which
requires X11 and is unmaintained, this reimplementation uses gtk4
instead.

Author: linkmauve

_data/projects.json

@@ -140,6 +140,10 @@
     "name": "relm",
     "url": "https://github.com/antoyo/relm"
   },
+  {
+    "name": "ScreenSelector.so",
+    "url": "https://linkmauve.fr/dev/screen-selector/"
+  },
   {
     "name": "Shortwave",
     "url": "https://gitlab.gnome.org/World/Shortwave",