Custom Fields: Add custom fields experimental setting.

[cbravobernal]

What?

Do not merge until 16.4 is released.
Adds an experimental setting for future Custom Fields proofs of concepts.

Why?

To start with experiments without interfere the Gutenberg experience until we have more stable things.

How?

Testing Instructions

Now is only the visual interface. Enabling this option won't cause anything yet.

Testing Instructions for Keyboard

Screenshots or screencast

[github-actions]

This pull request has changed or added PHP files. Please confirm whether these changes need to be synced to WordPress Core, and therefore featured in the next release of WordPress.

If so, it is recommended to create a new Trac ticket and submit a pull request to the WordPress Core Github repository soon after this pull request is merged.

If you're unsure, you can always ask for help in the #core-editor channel in WordPress Slack.

Thank you! ❤️

View changed files

❔ lib/experimental/editor-settings.php
❔ lib/experiments-page.php

[github-actions]

Flaky tests detected in 77047c3.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/5725199582
📝 Reported issues:

• [Flaky Test] should load styles added through enqueue_block_assets #53088 in specs/editor/plugins/iframed-equeue-block-assets.test.js

[cbravobernal]

Closed for #53241