Add `no_main` lint #148

Job	Run time
set-image	1s
clippy	2m 14s
spellcheck	1m 14s
clippy-examples (STD)	8m 49s
dylint	2m 19s
check (STD)	7m 22s
clippy-examples (WASM)	2m 28s
fmt	2m 2s
check (WASM)	1m 8s
check (RISCV)	1m 23s
examples-test	16m 3s
test	10m 50s
build (STD)	11m 48s
build (WASM)	1m 7s
docs	2m 20s
codecov	20m 54s
examples-docs	2m 42s
examples-contract-build (WASM)	15m 4s
examples-contract-build (RISCV)	2m 26s
measurements / contract-sizes	15m 59s
fuzz	0s
	2h 8m 13s

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