Fix control styles on the gallery settings page

[utkarshcloudinary]

The Layout control and the other custom controls on the gallery settings page showed the default browser button style. The controls did not get their styles.

The styles are in gallery.scss. Only the block editor imported this file. The settings page app did not import it, and the enqueued styles did not include it.

Approach

• Import gallery.scss in the settings page app (src/js/components/settings-gallery.js). The build makes css/gallery.css.
• Enqueue css/gallery.css on the gallery settings page (php/media/class-gallery.php).

Commit 0b0b520 removed the gallery.scss import from the settings page app.

QA notes

1. Connect the plugin to a Cloudinary account.
2. Go to Cloudinary > Gallery settings.
3. Open the Layout panel.
4. Make sure the four layout options (Expanded 1/2/3 Column, Classic) show as a list. Each option has an icon and a label. The options do not show the default browser button style.
5. Select a different layout option. Make sure the selected option gets the active color.
6. Make sure the preview on the right updates.