render react in demo component

src/demos/React/index.jsx

@@ -0,0 +1,40 @@
+import React, { Component } from 'react'
+import { Editor } from '@tiptap/core'
+import extensions from '@tiptap/starter-kit'
+
+export default class TestComponent extends Component {
+  constructor() {
+    super()
+    this.editorNode = React.createRef()
+  }
+  
+  componentDidMount() {
+    this.editor = new Editor({
+      element: this.editorNode.current,
+      content: '<p>rendered in <strong>react</strong>!</p>',
+      extensions: extensions(),
+    })
+    this.forceUpdate()
+  }
+
+  render() {
+    return (
+      <div>
+        {this.editor &&
+          <div>
+            <button onClick={() => this.editor.focus().removeMarks()}>
+              clear formatting
+            </button>
+            <button
+              onClick={() => this.editor.focus().bold()}
+              className={`${this.editor.isActive('bold') ? 'is-active' : ''}`}
+            >
+              bold
+            </button>
+          </div>
+        } 
+        <div ref={this.editorNode} />
+      </div>
+    )
+  }
+}