Added package oldgtk3 (#549)

packages.json

@@ -6863,6 +6863,20 @@
     "license": "GPLv3",
     "web": "https://gitlab.com/waylon531/tf2plug"
   },
+  {
+    "name": "oldgtk3",
+    "url": "https://github.com/stefansalewski/oldgtk3",
+    "method": "git",
+    "tags": [
+      "library",
+      "gtk",
+      "wrapper",
+      "gui"
+    ],
+    "description": "Low level bindings for GTK3 related libraries",
+    "license": "MIT",
+    "web": "https://github.com/stefansalewski/oldgtk3"
+  },
   {
     "name": "godot",
     "url": "https://github.com/pragmagic/godot-nim",