feat(routing)!: custom 3xx routes

[avevotsira]

Changes:

Part of : withastro/roadmap#1170

• similar to 404.astro, to have a 3xx.astro file that will serve any 3 hundred status code
• users can use any markup inside the page
• fallback to the built-in redirect layout if nothing is provided

Testing

• Added a test case of custom 3xx.astro with some custom HTML, and then assert that the redirect returns that custom HTML

Docs

This change requires updates to the docs.
/cc @withastro/maintainers-docs for feedback!

[changeset-bot]

⚠️ No Changeset found

Latest commit: 4032e38

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[codspeed-hq]

CodSpeed Performance Report

Merging #13827 will not alter performance

_{Comparing avevotsira:feat/personalised-3xx-page (4032e38) with main (304df34)}

Summary

✅ 6 untouched benchmarks