Add x-close button to block.

frontend/src/app/components/mempool-block/mempool-block.component.html

@@ -2,7 +2,7 @@
 
   <div class="title-block">
     <h1 class="float-left">{{ getGetOrdinal() }}</h1>
-    <button [routerLink]="['/' | relativeUrl]" class="btn btn-sm float-right mr-2">&#10005;</button>
+    <button [routerLink]="['/' | relativeUrl]" class="btn btn-sm float-right mr-2 mt-2">&#10005;</button>
   </div>
 
   <div class="clearfix"></div>