Optimized wiki code (#2566)

* optimized path component

* abstract component

* repair copy bug

* move copy&move&download to list-item

* add modal portal

frontend/src/components/modal-portal.js

@@ -0,0 +1,35 @@
+import React from 'react';
+import ReactDOM from 'react-dom';
+import PropTypes from 'prop-types';
+
+const propTypes = {
+  children: PropTypes.object.isRequired,
+};
+
+const modalRoot = document.getElementById('modal-wrapper');
+class ModalPortal extends React.Component {
+
+  constructor(props) {
+    super(props);
+    this.el = document.createElement('div');
+  }
+
+  componentDidMount() {
+    modalRoot.appendChild(this.el);
+  }
+
+  componentWillUnmount() {
+    modalRoot.removeChild(this.el);
+  }
+
+  render() {
+    return ReactDOM.createPortal(
+      this.props.children,
+      this.el,
+    );
+  }
+}
+
+ModalPortal.propTypes = propTypes;
+
+export default ModalPortal;