add iframe to demo content

docs/src/components/DemoContent/index.vue

@@ -0,0 +1,18 @@
+<template>
+  <div v-if="mainFile">
+    <component :is="mainFile" v-if="mode === 'vue'" />
+    <react-renderer :component="mainFile" v-if="mode === 'react'" />
+  </div>
+</template>
+
+<script>
+import DemoMixin from '~/components/DemoMixin'
+
+export default {
+  mixins: [DemoMixin],
+
+  components: {
+    ReactRenderer: () => import(/* webpackChunkName: "react-renderer" */ '~/components/ReactRenderer'),
+  },
+}
+</script>