Varia: migrate sass/blocks/heading

varia/sass/blocks/heading/_editor.scss

@@ -4,7 +4,8 @@
 .wp-block-heading h4, h4, .h4,
 .wp-block-heading h5, h5, .h5,
 .wp-block-heading h6, h6, .h6 {
-	font-family: #{map-deep-get($config-heading, "font", "family")};
+	font-family: #{map-deep-get($config-heading, "font", "family")}; // For browsers that don't support CSS variables.
+	font-family: var( --font-headings, #{map-deep-get($config-heading, "font", "family")} );
 	font-weight: #{map-deep-get($config-heading, "font", "weight")};
 	clear: both;
 }

varia/sass/blocks/heading/_style.scss

@@ -5,6 +5,7 @@ h4, .h4,
 h5, .h5,
 h6, .h6 {
 	font-family: #{map-deep-get($config-heading, "font", "family")};
+	font-family: var( --font-headings, #{map-deep-get($config-heading, "font", "family")} );
 	font-weight: #{map-deep-get($config-heading, "font", "weight")};
 	clear: both;
 }

varia/style-editor.css

@@ -358,6 +358,7 @@ object {
 .wp-block-heading h5, h5, .h5,
 .wp-block-heading h6, h6, .h6 {
 	font-family: sans-serif;
+	font-family: var(--font-headings, sans-serif);
 	font-weight: bold;
 	clear: both;
 }

varia/style-rtl.css

@@ -1041,6 +1041,7 @@ input[type="submit"],
 	cursor: pointer;
 	font-weight: bold;
 	font-family: sans-serif;
+	font-family: var(--font-headings, sans-serif);
 	font-size: 1.2rem;
 	background-color: blue;
 	border-radius: 9px;

varia/style.css

@@ -1385,6 +1385,7 @@ h4, .h4,
 h5, .h5,
 h6, .h6 {
 	font-family: sans-serif;
+	font-family: var(--font-headings, sans-serif);
 	font-weight: bold;
 	clear: both;
 }