Hide highlight on drag leave

src/DragGrid.vue

@@ -2,6 +2,7 @@
   <div
     @dragover.prevent="disabled ? undefined : handleDragOver($event)"
     @drop.prevent="disabled ? undefined : handleDrop($event)"
+    @dragleave="$refs.highlightContainer.style.display = 'none'"
     class="grid"
   >
     <div class="highlight-container" ref="highlightContainer">