[ui][textarea] add description prop

apps/storybook/stories/text-area.stories.tsx

@@ -15,6 +15,9 @@ export default {
     autoComplete: {
       control: 'text',
     },
+    description: {
+      control: 'text',
+    },
     disabled: {
       control: 'boolean',
     },
@@ -108,6 +111,20 @@ export function Error() {
   );
 }
 
+export function Description() {
+  const [value, setValue] = useState('Some comment');
+
+  return (
+    <TextArea
+      description="Your message must be at least 6 characters"
+      errorMessage={value.length < 6 ? 'Your comment is too short' : undefined}
+      label="Leave a reply"
+      value={value}
+      onChange={setValue}
+    />
+  );
+}
+
 export function ReadOnly() {
   return (
     <TextArea