[Hyperdrive] Document creating PlanetScale databases with Wrangler

[mtlemilio]

Summary

Adds relevant documentation for the new wrangler commands being added to support the PlanetScale partnership. cloudflare/workers-sdk#15065

Documentation checklist

• Is there a changelog entry (guidelines)? If you don't add one for something awesome and new (however small) — how will our customers find out? Changelogs are automatically posted to RSS feeds, the Discord, and X.
• The change adheres to the documentation style guide.

[cloudflare-docs-bot]

Review

✅ No issues found in commit c20f31f.

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