Docs: Add Preact code snippet for Whats a Story

docs/get-started/whats-a-story.md

@@ -27,6 +27,7 @@ Let’s start with the `Button` component. A story is a function that describes
     'web-components/button-story.js.mdx',
     'html/button-story.js.mdx',
     'html/button-story.ts.mdx',
+    'preact/button-story.js.mdx',
   ]}
 />
 

docs/snippets/preact/button-story.js.mdx

@@ -0,0 +1,14 @@
+```js
+// Button.stories.js|jsx
+
+/** @jsx h */
+import { h } from 'preact';
+import { Button } from './Button';
+
+export default {
+  title: 'Button',
+  component: Button,
+}
+
+export const Primary = () => <Button primary label='Button' />;
+```