docs(hydroflow_plus): add initial docs on consistency and safety (#1592) #957

Job	Run time
pre_job	6s
linux (x86_64-unknown-linux-gnu)	3m 39s
linux (i686-unknown-linux-gnu)	3m 33s
macos-universal (universal2-apple-darwin)	2m 40s
linux-cross (aarch64-unknown-linux-gnu, aarch64)	3m 32s
windows (x86_64-pc-windows-msvc, x64)	2m 32s
linux-cross (armv7-unknown-linux-gnueabihf, armv7)	3m 32s
windows (i686-pc-windows-msvc, x86)	2m 31s
windows (aarch64-pc-windows-msvc, x64)	2m 34s
Release	1s
	24m 40s

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