docs: update theme management cookbook

[forresst]

Update to enable dark mode

What is it?

• Docs

Description

The method for enabling dark mode was outdated. (I believe it was specific to Tailwind V2).

Now, after running pnpm run qwik add tailwind, you need to modify the global.css file to enable dark mode.

Checklist

• My code follows the developer guidelines of this project
• This is a documentation-only change (no changeset needed)

[changeset-bot]

⚠️ No Changeset found

Latest commit: 958a6cc

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

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@builder.io/qwik@8304

npm i https://pkg.pr.new/@builder.io/qwik-city@8304

npm i https://pkg.pr.new/eslint-plugin-qwik@8304

npm i https://pkg.pr.new/create-qwik@8304

commit: 958a6cc

[github-actions]

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Name	Status	Preview	Last Commit
qwik-docs	✅ Ready (View Log)	Visit Preview	958a6cc

[gioboa]

Thanks for your help @forresst 🚀