Add customizable keyboard shortcuts

[GregBrimble]

Description

Pending the release of Algolia's @docsearch/[email protected], which will add support for customizing keyboard shortcuts, this PR does the work to render these custom keyboard shortcuts in the @astrojs/starlight-docsearch component.

I'm now relying on the default rendering of these buttons for Ctrl/Cmd+K, but kept the familiar / rendering. Happy to change it too, but figured you'd probably prefer consistency where possible.

With all keyboard shortcuts disabled

With Ctrl/Cmd+K enabled

With / enabled

[changeset-bot]

⚠️ No Changeset found

Latest commit: 6d9d8e4

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

[netlify]

✅ Deploy Preview for astro-starlight ready!

Name	Link
🔨 Latest commit	6d9d8e4
🔍 Latest deploy log	https://app.netlify.com/projects/astro-starlight/deploys/68ba4f312931e00008096cb7
😎 Deploy Preview	https://deploy-preview-3410--astro-starlight.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
Lighthouse	1 paths audited Performance: 100 (no change from production) Accessibility: 100 (no change from production) Best Practices: 100 (no change from production) SEO: 100 (no change from production) PWA: - View the detailed breakdown and full score reports

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[astrobot-houston]

Hello! Thank you for opening your first PR to Starlight! ✨

Here’s what will happen next:

1. Our GitHub bots will run to check your changes.
   If they spot any issues you will see some error messages on this PR.
   Don’t hesitate to ask any questions if you’re not sure what these mean!

2. In a few minutes, you’ll be able to see a preview of your changes on Netlify 🤩

3. One or more of our maintainers will take a look and may ask you to make changes.
   We try to be responsive, but don’t worry if this takes a few days.