Fix --c-bg for editor.

[tcmulder]

You can find this implemented in Overture Promotions's core.php. Essentially, the code wasn't loaded in the iframe-ed editor, but this forced it to:

/**
 * Allow access to current background color var
 *
 * This let's you do things like:
 *	.thing {
*		border: 1px solid var(--c-bg);
* 	}
* So, for .thing.has-0-000-background-color
* you'll get a black border, and for
* .thing.has-0-900-background-color you'll
* get a white border, matching their respective
* backgrounds. It's often quite useful.
*/
function aquamin_bg_css() {
	$style_html = '';
	$colors = wp_get_global_settings( array( 'color', 'palette', 'theme' ) );
	$site_background = wp_get_global_styles( array( 'color', 'background' ) );
	if ( $colors ) {
		$styles = array( sprintf(
			':root,.is-root-container{--c-bg:%s;}/*%s*/', $site_background, __( 'Value of theme.json\'s styles.color.background' ) )
		);
		foreach( $colors as $color ) {
			array_push( $styles, sprintf(
				'.has-%s-background-color{--c-bg:var(--c-%s)}/*%s*/',
				$color[ 'slug' ],
				$color[ 'slug' ],
				$color[ 'name' ]
			) );
		}
		$style_html = implode( "\n", $styles );
	}
	return $style_html;
}

add_action( 'wp_enqueue_scripts', 'aquamin_bg_front_end', 50 );
function aquamin_bg_front_end() {
	$style_html = aquamin_bg_css();
	if ( $style_html ) {
		wp_add_inline_style( 'aquamin-style', $style_html );
	}
}

add_filter( 'block_editor_settings_all', 'aquamin_bg_back_end', 10,2 );
function aquamin_bg_back_end( $editor_settings, $editor_context ) {
	$style_html = aquamin_bg_css();
	if ( $style_html ) {
		$editor_settings["styles"][] = array( "css" => $style_html );
	}
	return $editor_settings;
}