Define `Warning` type and start annotating possible parse errors #400

Job	Run time
License / vulnerability audit (advisories)	53s
Test performance on benchmarks	35s
Clippy	24s
Enforce Rust code format	14s
License / vulnerability audit (bans licenses sources)	19s
Preflight docs.rs build	14s
Preflight crate publish (ubuntu-latest, stable)	23s
Unit tests with minimum versions of direct dependencies (windows-latest)	57s
Unit tests (windows-latest, stable)	1m 59s
Unit tests with minimum versions of direct dependencies (macos-latest)	34s
Unit tests (windows-latest, 1.74.0)	1m 7s
Check for unused dependencies	22s
Unit tests with minimum versions of direct dependencies (ubuntu-latest)	26s
Unit tests (macos-latest, stable)	26s
Unit tests (macos-latest, 1.74.0)	32s
Unit tests (ubuntu-latest, stable)	30s
Unit tests (ubuntu-latest, 1.74.0)	24s
	10m 19s

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