Add read-flash support #377

Job	Run time
Check MSRV (x86_64-unknown-linux-gnu)	28s
Check lib (x86_64-unknown-linux-gnu)	25s
Check MSRV (aarch64-unknown-linux-gnu)	1m 41s
Clippy (x86_64-unknown-linux-gnu)	27s
Check lib (aarch64-unknown-linux-gnu)	1m 16s
Check (x86_64-apple-darwin)	50s
Check MSRV (armv7-unknown-linux-gnueabihf)	1m 36s
Clippy (aarch64-unknown-linux-gnu)	1m 28s
Check lib (armv7-unknown-linux-gnueabihf)	1m 28s
Check (x86_64-unknown-linux-gnu)	20s
Clippy (armv7-unknown-linux-gnueabihf)	1m 33s
Check (x86_64-unknown-linux-musl)	28s
Rustfmt	6s
Check (x86_64-pc-windows-msvc)	2m 36s
Unit Tests (x86_64-unknown-linux-gnu)	39s
Check (aarch64-unknown-linux-gnu)	1m 41s
Unit Tests (aarch64-unknown-linux-gnu)	1m 36s
Check (armv7-unknown-linux-gnueabihf)	1m 43s
Unit Tests (armv7-unknown-linux-gnueabihf)	1m 21s
	21m 42s

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