feat: add Simple Layout without default styles and components

[totto2727]

Overview

• Addition of SimpleStarlightPage.astro file with non-user CSS styling and removal of all but the minimum required elements
• Extracted part of Page.astro into a separate component

Although the appearance has not been directly changed, the order in which the CSS is loaded may have changed.

Details

A StarlightPage component already exists that provides layouts for custom pages.
However, if you want to display content across the full screen, I don't need the header and sidebars included in StarlightPage.

ex. Reveal.js slides, etc.

However, it is troublesome to set up the head from scratch just for that custom page, and there is more code to manage.
If possible, it is preferable to have the same structure as the page using the StarlightPage component.

So I added a component that provides only the minimum layout required.

If you already have a solution to this problem, I would appreciate it if you could let me know.

[changeset-bot]

🦋 Changeset detected

Latest commit: c004dc0

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	Minor

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Tracked Files

Locale	File	Note
en	guides/pages.mdx	Source changed, localizations will be marked as outdated.
ja	guides/pages.mdx	Localization changed, will be marked as complete.

Warnings reference

Icon	Description
🔄️	The source for this localization has been updated since the creation of this pull request, make sure all changes in the source have been applied.

[Nadwey]

This component is named StarlightHeadlessPage, but it is referred to as SimpleStarlightPage elsewhere.

[Nadwey]

Suggested change

	[data-has-sidebar] {
	:global(:root[data-has-sidebar]) {