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feature: shadow mapping, directional and spot lights #504

Job	Run time
install-cargo-gpu (ubuntu-latest)	57s
renderling-test-linux	7m 54s
renderling-build-example	5m 3s
install-cargo-gpu (macos-latest)	52s
renderling-clippy	1m 24s
install-cargo-gpu (windows-latest)	3m 25s
renderling-test-macos	4m 16s
renderling-test-windows	4m 13s
renderling-build-shaders (ubuntu-latest)	3m 26s
renderling-build-shaders (macos-latest)	2m 56s
renderling-build-shaders (windows-latest)	3m 11s
	37m 37s

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