Allow using SVG images as project icon

Since exporters will save their own icon, the target platforms
don't have to support SVG to display the icon correctly.

This closes #23068.

main/main.cpp

@@ -1608,7 +1608,7 @@ Error Main::setup2(Thread::ID p_main_tid_override) {
 	GLOBAL_DEF("application/config/icon", String());
 	ProjectSettings::get_singleton()->set_custom_property_info("application/config/icon",
 			PropertyInfo(Variant::STRING, "application/config/icon",
-					PROPERTY_HINT_FILE, "*.png,*.webp"));
+					PROPERTY_HINT_FILE, "*.png,*.webp,*.svg,*.svgz"));
 
 	GLOBAL_DEF("application/config/macos_native_icon", String());
 	ProjectSettings::get_singleton()->set_custom_property_info("application/config/macos_native_icon",