Store typedef on the helper and use it to show a parameter list

site/components/Code.jsx

@@ -0,0 +1,26 @@
+import React, {PureComponent} from 'react';
+import {string} from 'prop-types';
+import {Prism as SyntaxHighlighter} from 'react-syntax-highlighter';
+import {coy} from 'react-syntax-highlighter/dist/styles/prism';
+
+class Code extends PureComponent {
+  render() {
+    let language = this.props.language;
+    if (!language) {
+      language = 'js';
+    }
+
+    return (
+      <SyntaxHighlighter language={language} style={coy}>
+        {this.props.value}
+      </SyntaxHighlighter>
+    );
+  }
+}
+
+Code.propTypes = {
+  value: string.isRequired,
+  language: string
+};
+
+export default Code;