Upgrading from Astro 2.0 to 3.0 (optional)

Upgrade docs:

• https://docs.astro.build/en/guides/upgrade-to/v3/

Breaking changes to know:

• Default port changed from 3000 to 4321: https://deploy-preview-4166—astro-docs-2.netlify.app/en/guides/upgrade-to/v3/#changed-default-port-3000
• Removed @astrojs/image: https://deploy-preview-4166—astro-docs-2.netlify.app/en/guides/upgrade-to/v3/#removed-astrojsimage
• Updated image docs: https://docs.astro.build/en/guides/images/
• HTTP request methods case changed (post -> POST): https://deploy-preview-4166—astro-docs-2.netlify.app/en/guides/upgrade-to/v3/#changed-http-request-methods-case
• Node 16 support removed (requires Node 18.14+): https://deploy-preview-4166—astro-docs-2.netlify.app/en/guides/upgrade-to/v3/#removed-support-for-node-16