Update layout, navigation, and content for documentation pages

Enhanced the documentation pages by updating the layout with aesthetic adjustments and adding better navigation elements. New documentation content was added: 'Authentication', 'Getting Started', and their child pages. This ensures users have a clearer path when viewing, navigating, and accessing the information they need. "Read more" fallback label was added to the documentation cards for better accessibility.

apps/web/app/(marketing)/docs/[...slug]/page.tsx

@@ -4,6 +4,7 @@ import { notFound } from 'next/navigation';
 
 import { ContentRenderer, createCmsClient } from '@kit/cms';
 import { If } from '@kit/ui/if';
+import { Separator } from '@kit/ui/separator';
 
 import { withI18n } from '~/lib/i18n/with-i18n';
 
@@ -56,7 +57,9 @@ async function DocumentationPage({ params }: PageParams) {
           <ContentRenderer content={page.content} />
         </article>
 
-        <If condition={page.children}>
+        <If condition={page.children.length > 0}>
+          <Separator />
+
           <DocsCards cards={page.children ?? []} />
         </If>
       </div>