Open external links in a new tab

[gronnerup]

Summary

Community request: external links in the catalog (Visit, and links generally) should open in a new browser tab instead of navigating away from the catalog.

Changes

• Added a small script in BaseLayout that flags every <a> pointing to a different origin with target="_blank" and rel="noopener noreferrer". One place, so it covers the Visit/Docs/Source actions, footer links (GitHub, CC-BY), the about/submit links, and links inside rendered tool descriptions.
• Internal links (tool/category pages, RSS, API) are unaffected and stay in the same tab.

Verification

• npx astro check -> 0 errors/warnings/hints.
• npm run build passes; confirmed the script ships inlined on home, tool-detail, and about pages.

Notes

• Chose a single origin-based script over editing every anchor: DRY, and it also handles external links inside markdown tool descriptions (which per-template edits would miss). Degrades gracefully without JS (links still work, same tab).