Add Multiple Windows Demo (#1103)

misc/multiple_windows/project.godot

@@ -0,0 +1,31 @@
+; Engine configuration file.
+; It's best edited using the editor UI and not directly,
+; since the parameters that go here are not all obvious.
+;
+; Format:
+;   [section] ; section goes between []
+;   param=value ; assign values to parameters
+
+config_version=5
+
+[application]
+
+config/name="Multiple Windows Demo"
+config/description="A demo showing all Window classes and their use within the main window."
+run/main_scene="res://scenes/main_scene.tscn"
+config/features=PackedStringArray("4.5", "GL Compatibility")
+run/low_processor_mode=true
+config/icon="res://icon.webp"
+
+[display]
+
+window/size/viewport_width=650
+window/size/viewport_height=650
+window/stretch/mode="canvas_items"
+window/stretch/aspect="expand"
+window/per_pixel_transparency/allowed=true
+
+[rendering]
+
+renderer/rendering_method="gl_compatibility"
+renderer/rendering_method.mobile="gl_compatibility"