Add markdown-it fix references

[cookesan]

Adds markdown-it fix references to GHSA-6v5v-wf23-fmfq.

Audit refresh, July 8, 2026:

• Confirmed the live PR is open, ready for review, merge-clean, and the visible advisory check is green.
• Rechecked the merge-base diff: exactly one advisory JSON file changes (advisories/github-reviewed/2026/06/GHSA-6v5v-wf23-fmfq/GHSA-6v5v-wf23-fmfq.json), JSON parses, git diff --check passes, and the exact-head worktree is clean.
• Revalidated the added public references and package-version evidence in the diff; all resolve through their source site or registry.

[cookesan]

Review note: this expands the markdown-it advisory with a fix commit and npm package-version reference, plus EOF newline normalization. Affected ranges, severity, and advisory metadata fields are unchanged. Commit 9ce2087562c45d1e5ddd9f76b990f4b3fbe040e5 resolves, and npm confirms markdown-it@14.2.0. The advisory JSON validates against the OSV schema.