Fix type mistake

Author: rakibhoossain

demo/vue3js.html

@@ -45,7 +45,7 @@ <h1>How to integrate GridStack.js with Vue.js</h1>
           ];
 
           onMounted(() => {
-            grid = GridStack.init({ // DO NOT user grid.value = GridStack.init(), see above
+            grid = GridStack.init({ // DO NOT use grid.value = GridStack.init(), see above
               float: true,
               cellHeight: "70px",
               minRow: 1,