dcterms:conformsTo and schema:accessibilityFeature metadata improvements

The plugin is now abole to insert dcterms:conformsTo data.

The schema:accessibilityFeature field has been updated to:

• Allow multiple values;
• Benefit from values completition to ensure correct spelling/case.

What's Changed

• added accessibilityHazard support by @lb803 in #8
• Add Heuristic Tools by @lb803 in #11
• Add a11y metadata and fix minor bugs by @lb803 in #12

Full Changelog: v0.1.11...v0.1.12