add react demo (WIP) to bubble menu

docs/src/demos/Extensions/BubbleMenu/React/index.jsx

@@ -0,0 +1,23 @@
+import React from 'react'
+import { useEditor, EditorContent } from '@tiptap/react'
+import { defaultExtensions } from '@tiptap/starter-kit'
+import './styles.scss'
+
+export default () => {
+  const editor = useEditor({
+    extensions: [
+      ...defaultExtensions(),
+    ],
+    content: `
+      <p>
+        Hey, try to select some text here. There will popup a menu for selecting some inline styles. Remember: you have full control about content and styling of this menu.
+      </p>
+    `,
+  })
+
+  return (
+    <div>
+      <EditorContent editor={editor} />
+    </div>
+  )
+}