Throw warning if `CHANGELOG.md` file has not been modified #4965

Job	Run time
no-std (stable, wasm32-unknown-unknown)	1m 26s
Check Rust stable on ubuntu with --all-targets --no-default-features	1m 9s
no-std (nightly, wasm32-unknown-unknown)	1m 32s
rustfmt	18s
Clippy	1m 16s
Check Rust stable on ubuntu with --all-targets	1m 8s
Test Rust nightly on windows-2022	0s
Check Rust stable on ubuntu with --all-targets --all-features	1m 12s
Test Rust stable on ubuntu with --profile test-release	10m 7s
Check Rust nightly on ubuntu with --all-targets --no-default-features	1m 15s
Test Rust stable on ubuntu with --profile test-release --doc	5m 40s
Check Rust nightly on ubuntu with --all-targets	1m 12s
Test Rust nightly on ubuntu with --profile test-release	11m 20s
Check Rust nightly on ubuntu with --all-targets --all-features	1m 14s
Test Rust nightly on ubuntu with --profile test-release --doc	6m 18s
	45m 7s

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