Site Editor: Add navigation panel back button slot

[david-szabo97]

Description

Create a slot for Navigation Panel Back Button (< Dashboard). Enables consumers to replace it with their own component.

How has this been tested?

Make sure everything works the same as before.

Test code to test the slot-fill functionality:

import {
	__experimentalMainDashboardButton as MainDashboardButton,
} from '@wordpress/interface';
import {
	__experimentalNavigationBackButton as NavigationBackButton,
} from '@wordpress/components';

......

<MainDashboardButton>
	<NavigationBackButton
		backButtonLabel={ __( 'Custom button' ) }
		className="edit-site-navigation-panel__back-to-dashboard"
		href="index.php"
	/>
</MainDashboardButton>

Types of changes

New feature

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR.

[david-szabo97]

In which file should we document the usage?

[github-actions]

Size Change: +9 B (0%)

Total Size: 1.19 MB

Filename	Size	Change
build/block-editor/index.js	133 kB	+5 B (0%)
build/block-library/index.js	147 kB	-1 B
build/components/index.js	171 kB	-1 B
build/edit-post/index.js	306 kB	-4 B (0%)
build/edit-site/index.js	22.8 kB	+10 B (0%)

ℹ️ View Unchanged

Filename	Size	Change
build/a11y/index.js	1.14 kB	0 B
build/annotations/index.js	3.77 kB	0 B
build/api-fetch/index.js	3.42 kB	0 B
build/autop/index.js	2.83 kB	0 B
build/blob/index.js	664 B	0 B
build/block-directory/index.js	8.71 kB	0 B
build/block-directory/style-rtl.css	943 B	0 B
build/block-directory/style.css	942 B	0 B
build/block-editor/style-rtl.css	11.2 kB	0 B
build/block-editor/style.css	11.1 kB	0 B
build/block-library/editor-rtl.css	8.91 kB	0 B
build/block-library/editor.css	8.91 kB	0 B
build/block-library/style-rtl.css	8.1 kB	0 B
build/block-library/style.css	8.1 kB	0 B
build/block-library/theme-rtl.css	792 B	0 B
build/block-library/theme.css	793 B	0 B
build/block-serialization-default-parser/index.js	1.87 kB	0 B
build/block-serialization-spec-parser/index.js	3.06 kB	0 B
build/blocks/index.js	48 kB	0 B
build/components/style-rtl.css	15.3 kB	0 B
build/components/style.css	15.3 kB	0 B
build/compose/index.js	9.89 kB	0 B
build/core-data/index.js	14.8 kB	0 B
build/data-controls/index.js	821 B	0 B
build/data/index.js	8.74 kB	0 B
build/date/index.js	11.2 kB	0 B
build/deprecated/index.js	768 B	0 B
build/dom-ready/index.js	571 B	0 B
build/dom/index.js	4.52 kB	0 B
build/edit-navigation/index.js	11.1 kB	0 B
build/edit-navigation/style-rtl.css	881 B	0 B
build/edit-navigation/style.css	885 B	0 B
build/edit-post/style-rtl.css	6.43 kB	0 B
build/edit-post/style.css	6.42 kB	0 B
build/edit-site/style-rtl.css	3.95 kB	0 B
build/edit-site/style.css	3.95 kB	0 B
build/edit-widgets/index.js	26.3 kB	0 B
build/edit-widgets/style-rtl.css	3.16 kB	0 B
build/edit-widgets/style.css	3.16 kB	0 B
build/editor/editor-styles-rtl.css	476 B	0 B
build/editor/editor-styles.css	478 B	0 B
build/editor/index.js	42.5 kB	0 B
build/editor/style-rtl.css	3.85 kB	0 B
build/editor/style.css	3.85 kB	0 B
build/element/index.js	4.62 kB	0 B
build/escape-html/index.js	735 B	0 B
build/format-library/index.js	6.86 kB	0 B
build/format-library/style-rtl.css	547 B	0 B
build/format-library/style.css	548 B	0 B
build/hooks/index.js	2.16 kB	0 B
build/html-entities/index.js	623 B	0 B
build/i18n/index.js	3.57 kB	0 B
build/is-shallow-equal/index.js	713 B	0 B
build/keyboard-shortcuts/index.js	2.52 kB	0 B
build/keycodes/index.js	1.94 kB	0 B
build/list-reusable-blocks/index.js	3.1 kB	0 B
build/list-reusable-blocks/style-rtl.css	476 B	0 B
build/list-reusable-blocks/style.css	476 B	0 B
build/media-utils/index.js	5.31 kB	0 B
build/notices/index.js	1.77 kB	0 B
build/nux/index.js	3.4 kB	0 B
build/nux/style-rtl.css	671 B	0 B
build/nux/style.css	668 B	0 B
build/plugins/index.js	2.56 kB	0 B
build/primitives/index.js	1.43 kB	0 B
build/priority-queue/index.js	790 B	0 B
build/redux-routine/index.js	2.83 kB	0 B
build/reusable-blocks/index.js	3.05 kB	0 B
build/rich-text/index.js	13.3 kB	0 B
build/server-side-render/index.js	2.77 kB	0 B
build/shortcode/index.js	1.69 kB	0 B
build/token-list/index.js	1.27 kB	0 B
build/url/index.js	4.06 kB	0 B
build/viewport/index.js	1.83 kB	0 B
build/warning/index.js	1.14 kB	0 B
build/wordcount/index.js	1.22 kB	0 B

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[Copons]

In which file should we document the usage?

@david-szabo97 Not familiar with it, but the previous slot (MainDashboardButton.Slot) and its documentation, was done in this PR: #22179.

I can see there are some leftovers from the previous implementation in the docs, I guess this is a time as good as any to clean them up and update them to the new version. 🙂

[Addison-Stavlo]

Tested with and w/o a fill and this works great! 🥳

[david-szabo97]

Updated to reuse MainDashboardButton. I'll update the docs as well.

[Addison-Stavlo]

This is great to see, its much more clean now using the MainDashboardButton.

Tests good w/ and w/o the fill. 👍 Il ✅ as soon as we get rid of the invalid export noted in my comment above.

[Copons]

This works fine!
I second @Addison-Stavlo request of removing the outdated export (which messes up the build, btw).
As it's a straightforward change, I'll preapprove this.