修复自定义指令lemon-contextmenu报错的问题

dist/demo.html

@@ -0,0 +1,10 @@
+<meta charset="utf-8">
+<title>index demo</title>
+<script src="./index.umd.js"></script>
+
+<link rel="stylesheet" href="./index.css">
+
+
+<script>
+console.log(index)
+</script>