Resolve "Implement basic functionality"

Closes #1 (closed) Closes #2 (closed) Closes #3 (closed) Closes #4 (closed) Closes #5 (closed) Closes #6 (closed)

example/src/App.vue

@@ -73,6 +73,11 @@ import NumberCounter from "./components/NumberCounter.vue";
         <template #item="item">
           <number-counter v-model="item.data.num"></number-counter>
         </template>
+        <template #highlight>
+          <div ref="highlight" class="custom-highlight">
+            Das hier ist das Highlight
+          </div>
+        </template>
       </drag-grid>
     </div>
     <div class="ttt-container">