Improve shadows and docs #602

Job	Run time
build (windows-latest)	7m 51s
build (ubuntu-latest)	3m 23s
check-bevy-internal-imports	6s
check-doc	7m 35s
build (macos-latest)	4m 26s
check-missing-examples-in-docs	29s
miri	7m 0s
ci	3m 8s
run-examples-on-windows-dx12	16m 13s
toml	8s
check-missing-features-in-docs	30s
markdownlint	2m 1s
check-compiles	3m 56s
msrv	2m 9s
build-wasm	1m 29s
	1h 0m 24s

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