Rainfall: Add black header post template

rainfall/templates/page-header-black.html

@@ -0,0 +1,47 @@
+<!-- wp:group {"style":{"elements":{"link":{"color":{"text":"var:preset|color|white"}}}},"backgroundColor":"black","textColor":"white"} -->
+<div class="wp-block-group has-white-color has-black-background-color has-text-color has-background has-link-color"><!-- wp:template-part {"slug":"header","tagName":"header"} /-->
+
+<!-- wp:group {"layout":{"inherit":true}} -->
+<div class="wp-block-group">
+	<!-- wp:group {"align":"wide"} -->
+	<div class="alignwide wp-block-group">
+		<!-- wp:columns -->
+		<div class="wp-block-columns"><!-- wp:column -->
+			<div class="wp-block-column"><!-- wp:post-title {"style":{"typography":{"textTransform":"uppercase"}}} /--></div>
+			<!-- /wp:column -->
+
+			<!-- wp:column -->
+			<div class="wp-block-column"><!-- wp:post-date {"textAlign":"right","format":"M j, Y","style":{"typography":{"textTransform":"uppercase"}}} /--></div>
+			<!-- /wp:column --></div>
+		<!-- /wp:columns -->
+	</div>
+	<!-- /wp:group -->
+	<!-- wp:spacer {"height":"12px"} -->
+	<div style="height:12px" aria-hidden="true" class="wp-block-spacer"></div>
+	<!-- /wp:spacer -->
+</div>
+<!-- /wp:group -->
+</div>
+<!-- /wp:group -->
+
+<!-- wp:post-featured-image /-->
+
+<!-- wp:group {"layout":{"inherit":true}} -->
+<div class="wp-block-group"><!-- wp:columns {"style":{"spacing":{"blockGap":"9.36rem"}}} -->
+	<div class="wp-block-columns"><!-- wp:column {"layout":{"inherit":false}} -->
+		<div class="wp-block-column"><!-- wp:post-content /-->
+
+			<!-- wp:group {"layout":{"type":"flex","flexWrap":"nowrap"}} -->
+			<div class="wp-block-group"><!-- wp:post-navigation-link {"type":"previous","showTitle":true,"linkLabel":true} /-->
+
+				<!-- wp:post-navigation-link {"showTitle":true,"linkLabel":true} /--></div>
+			<!-- /wp:group --></div>
+		<!-- /wp:column -->
+
+		<!-- wp:column {"width":"18rem"} -->
+		<div class="wp-block-column" style="flex-basis:18rem"><!-- wp:template-part {"slug":"sidebar"} /--></div>
+		<!-- /wp:column --></div>
+	<!-- /wp:columns --></div>
+<!-- /wp:group -->
+
+<!-- wp:template-part {"slug":"footer"} /-->

rainfall/theme.json

@@ -1,5 +1,14 @@
 {
 	"$schema": "https://schemas.wp.org/trunk/theme.json",
+	"customTemplates": [
+		{
+			"name": "page-header-black",
+			"postTypes": [
+				"page"
+			],
+			"title": "Page with black header"
+		}
+	],
 	"settings": {
 		"appearanceTools": true,
 		"color": {