Add withMarkdownNotes to storybook__addon-notes

Adding the option from
https://github.com/storybooks/storybook/pull/2946/files

types/storybook__addon-notes/index.d.ts

@@ -1,6 +1,7 @@
 // Type definitions for @storybook/addon-notes 3.3
 // Project: https://github.com/storybooks/storybook
 // Definitions by: Joscha Feth <https://github.com/joscha>
+//                 A.MacLeay <https://github.com/amacleay>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.6
 
@@ -8,6 +9,7 @@ import * as React from 'react';
 import { RenderFunction } from '@storybook/react';
 
 export function withNotes(textOrOptions: string | object): (getStory: RenderFunction) => RenderFunction;
+export function withMarkdownNotes(text: string): (getStory: RenderFunction) => RenderFunction;
 
 export interface WithNotesProps extends React.HTMLProps<HTMLDivElement> {
     notes?: string;

types/storybook__addon-notes/storybook__addon-notes-tests.tsx

@@ -1,7 +1,13 @@
 import * as React from 'react';
 
 import { storiesOf } from '@storybook/react';
-import { withNotes, WithNotes } from '@storybook/addon-notes';
+import { withNotes, withMarkdownNotes, WithNotes } from '@storybook/addon-notes';
+
+const SIMPLE_MARKDOWN = `
+## Markdown for component
+
+A very simple component with markdown notes
+`;
 
 storiesOf('Component', module)
   .add('with some emoji', () => (
@@ -13,4 +19,9 @@ storiesOf('Component', module)
     withNotes('A very simple component')(
       () => (<div>my component</div>)
     )
+  )
+  .add('with withMarkdownNotes',
+    withMarkdownNotes(SIMPLE_MARKDOWN)(
+      () => (<div>my component</div>)
+    )
   );