Add note about current development state #661

Job	Run time
Check lib (x86_64-unknown-linux-gnu)	29s
Check (x86_64-apple-darwin)	43s
Clippy (x86_64-unknown-linux-gnu)	52s
Check lib (aarch64-unknown-linux-gnu)	1m 55s
Check (x86_64-unknown-linux-gnu)	24s
Clippy (aarch64-unknown-linux-gnu)	3m 22s
Check lib (armv7-unknown-linux-gnueabihf)	1m 37s
Check (x86_64-unknown-linux-musl)	34s
Clippy (armv7-unknown-linux-gnueabihf)	2m 9s
Check (x86_64-pc-windows-msvc)	1m 25s
Check (aarch64-unknown-linux-gnu)	2m 24s
Check lib MSRV (x86_64-unknown-linux-gnu)	37s
Check (armv7-unknown-linux-gnueabihf)	2m 57s
Rustfmt	9s
Check lib MSRV (aarch64-unknown-linux-gnu)	2m 0s
Unit Tests (x86_64-unknown-linux-gnu)	58s
Check lib MSRV (armv7-unknown-linux-gnueabihf)	1m 43s
Unit Tests (aarch64-unknown-linux-gnu)	2m 54s
Unit Tests (armv7-unknown-linux-gnueabihf)	2m 46s
	29m 58s

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