Fix canvas resolution on high-DPI screens

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

@@ -1,5 +1,5 @@
 <div class="mempool-block-overview">
-  <canvas class="block-overview" #blockCanvas></canvas>
+  <canvas class="block-overview" [style.width]="cssWidth + 'px'" [style.height]="cssHeight + 'px'" #blockCanvas></canvas>
   <div class="loader-wrapper" [class.hidden]="!(isLoading$ | async)">
     <div class="spinner-border ml-3 loading" role="status"></div>
   </div>