Migration of Gitlab lint, check, workspace, examples stages to GitHub Actions #13

Job	Run time
set-image	2s
clippy	9m 4s
clippy-examples (STD)	12m 9s
check (STD)	9m 42s
dylint	4m 29s
clippy-examples (WASM)	3m 13s
check (WASM)	1m 49s
fmt	2m 59s
check (RISCV)	1m 39s
spellcheck	1m 46s
examples-test	17m 32s
test	14m 46s
build (STD)	20m 41s
build (WASM)	2m 39s
docs	12m 26s
codecov	37m 6s
examples-docs	4m 20s
examples-contract-build (WASM)	24m 48s
examples-contract-build (RISCV)	3m 16s
	3h 4m 26s

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