add: support sdl3 + opengl 3.3 and opengles 3.0

demo/sdl3_opengl3_opengles3/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.16)
+project(nuklear_sdl3
+    DESCRIPTION "nuklear_sdl3: Nuklear Immediate Mode GUI for SDL3"
+    HOMEPAGE_URL "https://github.com/Immediate-Mode-UI/Nuklear/"
+    LANGUAGES C
+)
+
+
+#  glad
+add_subdirectory(glad)
+target_include_directories(glad PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/glad/include)
+# nuklear
+add_library(nuklear INTERFACE)
+target_include_directories(nuklear INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/../..)
+
+# nuklear_sdl3
+add_library(nuklear_sdl3 INTERFACE)
+target_include_directories(nuklear_sdl3 INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})
+
+set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
+
+find_package(SDL3 REQUIRED)
+
+add_executable(nuklear_sdl3_ogl3
+    nuklear_sdl3_ogl3.c
+)
+
+target_link_libraries(nuklear_sdl3_ogl3 PUBLIC
+    nuklear
+    nuklear_sdl3
+    SDL3::SDL3
+    glad
+)
+
+
+set_property(DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY VS_STARTUP_PROJECT "nuklear_sdl3_ogl3")
+
+
+set_property(TARGET nuklear_sdl3_ogl3 PROPERTY C_STANDARD 99)

demo/sdl3_opengl3_opengles3/README.md

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+# SDL3 OpenGL/ES 3.x Example with Nuklear
+
+
+- This is a simple example demonstrating how to use SDL3 with OpenGL 3.x or OpenGL ES 3.x along with the Nuklear immediate mode GUI library, it can be compiled for desktop, web or mobile platforms.

demo/sdl3_opengl3_opengles3/cmake/FindSDL3.cmake

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+include(FetchContent)
+FetchContent_Declare(
+    SDL3
+    GIT_REPOSITORY  https://github.com/libsdl-org/SDL.git
+    GIT_TAG         release-3.2.4
+    GIT_SHALLOW     TRUE
+)
+FetchContent_MakeAvailable(SDL3)
+

demo/sdl3_opengl3_opengles3/glad/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.18)
+
+project(glad)
+
+add_library(glad STATIC)
+
+target_sources(glad PRIVATE src/glad.c)
+target_include_directories(glad PUBLIC include)