Insert temporary documentation hard-links as a solution to #575 until https://github.com/rust-lang/rust/issues/120983 is fixed. #858

Job	Run time
build (1.56.0, armv7a-none-eabi)	3m 9s
test (i686-unknown-linux-gnu, 1.56.0, sudo apt update && sudo apt install gcc-multilib)	3m 51s
build (1.56.0, thumbv7em-none-eabi)	3m 7s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	39s
build (1.56.0, wasm32-unknown-unknown)	3m 10s
test (x86_64-unknown-linux-gnu, 1.56.0)	3m 31s
test (x86_64-unknown-linux-gnu, stable)	41s
build (stable, armv7a-none-eabi)	7s
build (stable, thumbv7em-none-eabi)	5s
build (stable, wasm32-unknown-unknown)	18s
	18m 38s

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