add sdl3 backend

[avitran0]

adds an sdl3 backend. now properly builds, with code style etc.

also updated lwjgl to 3.4.1 (latest stable) for sdl bindings.

closes #314

[SpaiR]

Thanks for the contribution! 🙏

The PR looks solid, but it seems you've ported the backend version from the main branch. Since this binding uses the docking branch (which supports multi-viewports), you'll need to provide ImGuiPlatformIO implementations.

You can find a reference in the official C++ SDL3 backend here:
imgui_impl_sdl3.cpp#L1042

And here is how it's implemented for GLFW in this repo:
ImGuiImplGlfw.java#L1488

Once that's done, what do you think about extending the Application class to provide a usage example? We could add a new field to the Configuration class to select the preferred backend (keeping GLFW as the default) and initialize the corresponding backend here.

[avitran0]

aye sure, will take a look at that. thanks!