Switch CI from GitLab to GitHub Actions #11

Job	Run time
set-image	4s
bench-rust-nightly (bit-vec)	17m 24s
bench-rust-nightly (bytes)	16m 5s
checks	1m 20s
clippy	1m 13s
bench-rust-nightly (generic-array)	15m 54s
miri (bit-vec)	49m 47s
bench-rust-nightly (derive)	16m 25s
miri (bytes)	2m 35s
tests	1m 49s
bench-rust-nightly (max-encoded-len)	15m 59s
miri (generic-array)	2m 34s
miri (arbitrary)	2m 38s
build-linux-ubuntu-amd64	1m 17s
publish-dry-run	1m 19s
publish-crate	0s
	2h 26m 23s

Provide feedback