add codemirror

repl/src/CodeMirror.tsx

@@ -0,0 +1,14 @@
+import React from 'react';
+import { Controlled as CodeMirror2 } from 'react-codemirror2';
+import 'codemirror/mode/javascript/javascript.js';
+import 'codemirror/theme/material.css';
+import 'codemirror/lib/codemirror.css';
+
+export default function CodeMirror({ value, onChange, options }: any) {
+  options = options || {
+    mode: 'javascript',
+    theme: 'material',
+    lineNumbers: true,
+  };
+  return <CodeMirror2 value={value} options={options} onBeforeChange={onChange} />;
+}