Docs: Persist custom theme

[dimfeld]

This is stacked on top of #320 so currently includes changes from both.

This still needs a little more work, or we may want to drop this in favor of a better solution that addresses these pain points:

• The theme is saved, but when you reload the page custom themes are not applied unless you go back to the theme page and reenable preview. I think if we want to re-apply on startup it may require some higher-level integration of the custom theme.
• It now always says custom instead of the actual theme name... probably need to persist the selected theme value as well or something so we can reload that when it's not custom.

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: c4965497a01cf68bc3bbae4a3d09908953e2aebb

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

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

[vercel[bot]]

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

Name	Status	Preview	Comments	Updated (UTC)
svelte-ux	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Mar 31, 2024 4:46am