add example for sdlgpu3 support

backend_test/example_sdlgpu3_fetchcontent/CMakeLists.txt

@@ -0,0 +1,30 @@
+cmake_minimum_required(VERSION 3.30)
+project(cimgui_sdlgpu3 LANGUAGES C CXX)
+
+set(CMAKE_C_STANDARD 11)
+
+include(FetchContent)
+
+FetchContent_Declare(
+	sdl3
+	URL https://github.com/libsdl-org/SDL/releases/download/release-3.2.8/SDL3-3.2.8.tar.gz
+)
+
+FetchContent_MakeAvailable(sdl3)
+
+include(GenerateCimguiBindings.cmake)
+
+GenerateCimguiBindings(cimgui_with_backend)
+
+add_executable(${PROJECT_NAME} 
+	main.c
+)
+
+target_link_libraries(${PROJECT_NAME} PRIVATE SDL3::SDL3 cimgui_with_backend)
+target_compile_definitions(
+	${PROJECT_NAME}
+	PRIVATE 
+	CIMGUI_DEFINE_ENUMS_AND_STRUCTS=1
+	CIMGUI_USE_SDL3=1
+	CIMGUI_USE_SDLGPU3=1
+)