created a footer only template (#5103)

blockbase/block-templates/footer-only.html

@@ -0,0 +1,3 @@
+<!-- wp:post-content {"layout":{"inherit":true}} /-->
+
+<!-- wp:template-part {"slug":"footer","tagName":"footer","layout":{"inherit":true},"className":"site-footer-container"} /--> 

blockbase/theme.json

@@ -27,7 +27,15 @@
 				"page",
 				"post"
 			]
-		}
+		},
+        {
+            "name": "footer-only",
+            "title": "Footer Only",
+            "postTypes": [
+                "page",
+                "post"
+            ]
+        }
 	],
 	"settings": {
 		"border": {