Tooltip-style tx previews in block overview

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

@@ -1,6 +1,12 @@
 <div class="block-overview-graph">
-  <canvas class="block-overview-canvas" #blockCanvas></canvas>
+  <canvas class="block-overview-canvas" [class.clickable]="!!hoverTx" #blockCanvas></canvas>
   <div class="loader-wrapper" [class.hidden]="!isLoading">
     <div class="spinner-border ml-3 loading" role="status"></div>
   </div>
+
+  <app-block-overview-tooltip
+    [tx]="selectedTx || hoverTx"
+    [cursorPosition]="tooltipPosition"
+    [clickable]="!!selectedTx"
+  ></app-block-overview-tooltip>
 </div>