Geologist: add flex layout to header

geologist/block-template-parts/header.html

@@ -1,4 +1,4 @@
-<!-- wp:group {"tagName":"header","style":{"spacing":{"padding":{"bottom":"90px"}}},"className":"site-header"} -->
+<!-- wp:group {"tagName":"header","style":{"spacing":{"padding":{"bottom":"90px"}}},"className":"site-header","layout":{"type":"flex"}} -->
 <header class="wp-block-group site-header" style="padding-bottom:90px">
 	<!-- wp:site-logo /-->
 	<!-- wp:site-title /-->