make imgui include path flexible #77

Job	Run time
clang-format (Tetragrama) / clang-format	15s
clang-format (ZEngine) / clang-format	18s
macOS / cmake-build (Debug, x64) / cmake-build-macOS-x64-Debug	3m 11s
macOS / cmake-build (Release, x64) / cmake-build-macOS-x64-Release	3m 10s
macOS / cmake-build (Release, arm64) / cmake-build-macOS-arm64-Release	2m 50s
macOS / cmake-build (Debug, arm64) / cmake-build-macOS-arm64-Debug	2m 58s
windows / cmake-build (Release) / cmake-build-windows-Release	7m 52s
windows / cmake-build (Debug) / cmake-build-windows-Debug	7m 40s
macOS / test	0s
macOS / deploy	-1s
windows / deploy	-1s
windows / test	-1s
	28m 11s

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