Added Rational Curves #16

Job	Run time
check-bevy-internal-imports	4s
check-doc	6m 56s
build (windows-latest)	5m 17s
check-missing-examples-in-docs	33s
build (ubuntu-latest)	1m 54s
build (macos-latest)	3m 26s
ci	34s
miri	6m 43s
run-examples-on-windows-dx12	13m 2s
toml	7s
check-missing-features-in-docs	32s
check-compiles	0s
markdownlint	1m 37s
msrv	51s
build-wasm	32s
	42m 8s

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