ci: add Dockerfile for Railway compile-test #16

Job	Run time
cross_test/i686-unknown-linux-gnu/stable	1m 27s
native-backend/stable	56s
clippy/stable	21s
format/stable	9s
Pass MSRV values to other jobs	4s
nostd/thumbv6m-none-eabi/stable	9s
cross_test/s390x-unknown-linux-gnu/stable	1m 25s
docs/nightly	0s
miri	0s
cargo-careful	0s
tests/beta	1m 31s
blas-msrv	25s
tests/stable	1m 37s
tests/1.64.0	1m 45s
conclusion	-1s
	9m 48s

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