Migration of Gitlab lint, check, workspace, examples stages to GitHub Actions #9

Job	Run time
dylint	6m 12s
clippy	4m 37s
check (STD)	10m 31s
clippy-examples (STD)	14m 54s
check (WASM)	1m 27s
clippy-examples (WASM)	3m 40s
fmt	2m 47s
spellcheck	1m 50s
check (RISCV)	1m 34s
examples-test	16m 1s
build (STD)	3m 31s
test	15m 54s
build (WASM)	2m 16s
examples-contract-build (WASM)	24m 41s
examples-contract-build (RISCV)	3m 18s
examples-docs	4m 10s
codecov	32m 19s
docs	6m 9s
	2h 35m 51s

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