Add smallpt as an example notebook (#235) #1352

Job	Run time
emscripten_wasm (ubu24, ubuntu-24.04-arm, 3.1.45, bash)	2m 6s
build (ubu24, ubuntu-24.04, bash)	1m 27s
emscripten_wasm (osx15-arm, macos-15, 3.1.45, bash)	3m 41s
build (ubu24-arm, ubuntu-24.04-arm, bash)	1m 6s
build (ubu24-analyzers, ubuntu-24.04, true, -DCMAKE_BUILD_TYPE=Debug, bash)	4m 40s
build (ubu22, ubuntu-22.04, bash)	1m 26s
build (ubu22-arm, ubuntu-22.04-arm, bash)	1m 12s
build (osx13-x86, macos-13, bash)	2m 24s
build (osx14-arm, macos-14, bash)	1m 16s
build (osx15-arm, macos-15, bash)	1m 9s
build (Windows22, windows-2022, cmd.exe)	3m 35s
build (Windows25, windows-2025, cmd.exe)	2m 19s
	26m 21s

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