Use light page background for text layouts

styles/31-patterns-text-layouts.css

@@ -2,6 +2,16 @@
 /* Patterns: Text Layouts                                    */
 /* ========================================================= */
 
+.sg-page-text-layouts {
+  background: var(--surface-form-preview);
+  color: var(--color-font-dark);
+}
+
+.sg-page-text-layouts .sg-main-heading,
+.sg-page-text-layouts .sg-preview-label {
+  color: var(--color-font-dark);
+}
+
 .sg-text-layout-pattern {
   display: flex;
   flex-direction: column;