Update localizedUrl() to handle .html routes correctly

[delucis]

Description

• Closes Language Select incorrectly appends locale when switching index pages #1423
• Adds test cases for our localizedUrl() helper for routes with .html extensions
• Fixes the tests
• This fixes URLs in language picker (and a couple other places) for sites with build.format: 'file'

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Updated (UTC)
starlight	✅ Ready (Inspect)	Visit Preview	Jan 30, 2024 6:09pm

1 Ignored Deployment

Name	Status	Preview	Updated (UTC)
starlight-i18n	⬜️ Ignored (Inspect)		Jan 30, 2024 6:09pm

[astrobot-houston]

size-limit report 📦

Path	Size
/index.html	5.22 KB (0%)
/_astro/*.js	21.54 KB (0%)
/_astro/*.css	13.14 KB (0%)

[changeset-bot]

🦋 Changeset detected

Latest commit: 6fd4513

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@astrojs/starlight	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[delucis]

Going to merge this to get a patch release out — would still love any feedback if folks have it and we can always make follow-up PRs!