Imgui version requirements and necessary changes

[spiderkeys]

Hello, and thank you for this very helpful integration!

We use Conan to pull in all of our dependencies, including Imgui and implot. I was able to get qrhiimgui2 working fairly painlessly with Qt 6.7 where Qt was pulled in via Conan, but when trying to use a Conan-provided imgui 1.88, instead of the copy bundled in this repo, I got corrupted renderings that just looked like a smattering of multi colored dots.

Are there any specific constraints around imgui version, or configuration changes/code changes required to make things work? I did make sure that the one define in imgui_config.h was set (required to compile), but didn't see anything else that was immediately obvious.

Appreciate any insight you might be able to provide, and thanks for writing and publishing this library!

[Sayter99]

I am using bazel with Qt 6.5.3, ImGui 1.90.8, and the latest qrhiimgui2, it works well.
Perhaps try modifying hdrWhiteLevelMultiplier to see if there's better parameter for your environment, e.g. renderer->prepare(rhi, rt, cb, mvp, opacity, hdrWhiteLevelMultiplier /* <-- set to 1.0 */);