Added header template copied from Block Canvas and modified to match design.

decibel/parts/header.html

@@ -0,0 +1,25 @@
+<!-- wp:group {"layout":{"inherit":"true"},"style":{"spacing":{"padding":{"bottom":"var(--wp--style--root--padding-left)","top":"var(--wp--style--root--padding-left)"}}}} -->
+<div class="wp-block-group" style="padding-bottom:var(--wp--style--root--padding-left);padding-top:var(--wp--style--root--padding-left)">
+	<!-- wp:group {"align":"full","layout":{"type":"flex","justifyContent":"space-between","flexWrap":"nowrap","verticalAlignment":"top"}} -->
+	<div class="wp-block-group alignfull">
+	
+		<!-- wp:group {"layout":{"type":"flex"}} -->
+		<div class="wp-block-group">
+			<!-- wp:site-logo {"width":64} /-->
+	
+			<!-- wp:group {"style":{"spacing":{"blockGap":"0px"}}} -->
+			<div class="wp-block-group">
+				<!-- wp:site-title /-->
+				<!-- wp:site-tagline /-->
+			</div>
+			<!-- /wp:group -->
+		</div>
+		<!-- /wp:group -->
+	
+		<!-- wp:navigation {"__unstableLocation":"primary","layout":{"type":"flex","setCascadingProperties":true,"justifyContent":"right","orientation":"horizontal"},"style":{"spacing":{"margin":{"top":"0"}}}} /-->
+	
+	</div>
+	<!-- /wp:group -->
+
+</div>
+<!-- /wp:group -->