Editor: add support for block-level link hover colors.

Adds the ability to set link hover colors for individual blocks from the block inspector color panel.

Props @youknowriad, @peterwilsoncc, @kebbet.
Fixes #58575.

Built from https://develop.svn.wordpress.org/trunk@56028


git-svn-id: http://core.svn.wordpress.org/trunk@55540 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-theme-json.php

@@ -360,6 +360,9 @@ class WP_Theme_JSON {
 			'duotone'          => null,
 			'gradients'        => null,
 			'link'             => null,
+			'heading'          => null,
+			'button'           => null,
+			'caption'          => null,
 			'palette'          => null,
 			'text'             => null,
 		),
@@ -562,6 +565,9 @@ class WP_Theme_JSON {
 		array( 'border', 'style' ),
 		array( 'border', 'width' ),
 		array( 'color', 'link' ),
+		array( 'color', 'heading' ),
+		array( 'color', 'button' ),
+		array( 'color', 'caption' ),
 		array( 'dimensions', 'minHeight' ),
 		array( 'position', 'sticky' ),
 		array( 'spacing', 'blockGap' ),