Introduce HasSpan trait (#20) #68

Job	Run time
Unit tests (windows-latest, stable)	48s
Preflight crate publish (ubuntu-latest, stable)	23s
Clippy	17s
Unit tests (windows-latest, 1.72.0)	37s
Enforce Rust code format	12s
Unit tests (macos-latest, stable)	32s
Unit tests (macos-latest, 1.72.0)	2m 36s
Unit tests with minimum versions of direct dependencies (windows-latest)	35s
Preflight docs.rs build	16s
Unit tests with minimum versions of direct dependencies (macos-latest)	34s
Unit tests (ubuntu-latest, stable)	23s
Unit tests with minimum versions of direct dependencies (ubuntu-latest)	15s
Unit tests (ubuntu-latest, 1.72.0)	20s
License / vulnerability audit (advisories)	15s
License / vulnerability audit (bans licenses sources)	16s
Check for unused dependencies	19s
	8m 38s

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