feat: image-alt-missing — opt-in, WCAG-aware, default off (MD045) - #12

scripts/fixtures/defects-structure.md:25:11 MD034/no-bare-urls Bare URL used [Context: "https://example.com/dangling"] https://github.com/DavidAnson/markdownlint/blob/v0.41.1/doc/md034.md

scripts/fixtures/defects-structure.md:23:5 MD052/reference-links-images Reference links and images should use a label that is defined [Missing link or image reference definition: "no-def"] [Context: "[broken ref][no-def]"] https://github.com/DavidAnson/markdownlint/blob/v0.41.1/doc/md052.md

scripts/fixtures/defects-structure.md:21:9 MD056/table-column-count Table column count [Expected: 2; Actual: 3; Too many cells, extra data will be missing] https://github.com/DavidAnson/markdownlint/blob/v0.41.1/doc/md056.md

scripts/fixtures/defects-structure.md:9:9 MD051/link-fragments Link fragments should be valid [Expected: #skipped-level-h1-to-h3; Actual: #Skipped-level-h1-to-h3] [Context: "[a case mismatch](#Skipped-level-h1-to-h3)"] https://github.com/DavidAnson/markdownlint/blob/v0.41.1/doc/md051.md

scripts/fixtures/defects-structure.md:7:9 MD051/link-fragments Link fragments should be valid [Context: "[a missing anchor](#no-such-heading)"] https://github.com/DavidAnson/markdownlint/blob/v0.41.1/doc/md051.md

scripts/fixtures/defects-structure.md:5 MD025/single-title/single-h1 Multiple top-level headings in the same document [Context: "Second top-level title"] https://github.com/DavidAnson/markdownlint/blob/v0.41.1/doc/md025.md

scripts/fixtures/defects-structure.md:3 MD001/heading-increment Heading levels should only increment by one level at a time [Expected: h2; Actual: h3] https://github.com/DavidAnson/markdownlint/blob/v0.41.1/doc/md001.md

scripts/fixtures/decoy-clean.md:40:14 MD056/table-column-count Table column count [Expected: 2; Actual: 1; Too few cells, row will be missing data] https://github.com/DavidAnson/markdownlint/blob/v0.41.1/doc/md056.md

scripts/fixtures/decoy-clean.md:32 MD003/heading-style Heading style [Expected: atx; Actual: setext] https://github.com/DavidAnson/markdownlint/blob/v0.41.1/doc/md003.md