fix(storybook): move markdown.css to ui-components (#7581)

Author: avivkeller

apps/site/styles/index.css

@@ -7,6 +7,5 @@
 */
 
 @import '@node-core/ui-components/styles/index.css';
-@import './markdown.css';
 @import './effects.css';
 @import './locales.css';

packages/ui-components/styles/index.css

@@ -11,3 +11,4 @@
 @import 'tailwindcss/utilities';
 @import './effects.css';
 @import './base.css';
+@import './markdown.css';