Fix the WordPress.org plugin preview on trunk

[dkotter]

Description of the Change

Bringing changes from #143 over to trunk to get those deployed to WordPress.org

How to test the Change

The WordPress Playground allows you to spin up a new environment directly through the URL, by going to https://playground.wordpress.net/# and pasting your JSON config after the #. In this case, the URL should be:

https://playground.wordpress.net/#{"$schema":"https://playground.wordpress.net/blueprint-schema.json","landingPage":"/wp-admin/post.php?post=4&action=edit","preferredVersions":{"php":"7.4","wp":"latest"},"phpExtensionBundles":["kitchen-sink"],"steps":[{"step":"login","username":"admin","password":"password"},{"step":"installPlugin","pluginZipFile":{"resource":"wordpress.org/plugins","slug":"retro-winamp-block"},"options":{"activate":true}},{"step":"importWxr","file":{"resource":"url","url":"https://raw.githubusercontent.com/10up/retro-winamp-block/d2ff63d1127713d9f2a11235a002f38f2927b0ca/.wordpress-org/blueprints/demo-data.xml"}}]}

Changelog Entry

Fixed - Ensure the WordPress.org plugin preview works as expected

Credits

Props @dkotter

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.