VER conformance fixture corpus

Ninety-five executable fixtures: one per issue code, with the expected verdict recorded in a manifest.

1. OverviewMachine-checkable test vectors for the VER record format and the conformance profile implemented by packages/ver-validator.
2. Layoutvalid/ and invalid/ hold fixtures;
3. Running the corpusAgainst a single fixture, with the validator CLI.
4. The manifest contractcorpus names the newest release the corpus covers, not the only one: default_schema stays 1.0.1, so an entry that names no schema is still a statement about 1.0.1 and the existing fixtures are untouched.
5. Fixture construction rulesThese rules are what make a fixture a test vector rather than a sample.
6. 1.1-draft fixturesUnratified.
7. Relationship to the published artifactsFixtures target two artifact releases.