Refs #25217 - Refactor Markdown prop-types

* Adds default-props
* Convert to functional component

webpack/stories/components/Markdown/Markdown.js

@@ -4,30 +4,32 @@ import hljs from 'highlight.js';
 import Remarkable from 'react-remarkable';
 import './Markdown.scss';
 
-class Markdown extends React.Component {
-  render() {
-    const options = {
-      html: true,
-      breaks: true,
-      linkTarget: '_parent',
-      highlight(code, lang) {
-        if (lang !== undefined) {
-          return hljs.highlight(lang, code).value;
-        }
-        return '';
-      },
-    };
+const Markdown = ({ source }) => {
+  const options = {
+    html: true,
+    breaks: true,
+    linkTarget: '_parent',
+    highlight(code, lang) {
+      if (lang !== undefined) {
+        return hljs.highlight(lang, code).value;
+      }
+      return '';
+    },
+  };
 
-    return (
-      <div className="markdown-body">
-        <Remarkable source={this.props.source} options={options}/>
-      </div>
-    );
-  }
-}
+  return (
+    <div className="markdown-body">
+      <Remarkable source={source} options={options} />
+    </div>
+  );
+};
 
 Markdown.propTypes = {
   source: PropTypes.string,
 };
 
+Markdown.defaultProps = {
+  source: '',
+};
+
 export default Markdown;