add SDL3 repository to game engine

examples/categories.txt

@@ -1,14 +1,14 @@
-# Blank lines and lines that start with '#' in this file are ignored.
-
-# Categories, by directory name, go in here, in the order they should be
-# listed on the main page. If this file is missing, it'll assume any
-# subdirectory is a category and sort them alphabetically.
-
-renderer
-input
-audio
-camera
-asyncio
-pen
-misc
-demo
+# Blank lines and lines that start with '#' in this file are ignored.
+
+# Categories, by directory name, go in here, in the order they should be
+# listed on the main page. If this file is missing, it'll assume any
+# subdirectory is a category and sort them alphabetically.
+
+renderer
+input
+audio
+camera
+asyncio
+pen
+misc
+demo