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/content/documentation/authentication/authentication.mdoc

@@ -0,0 +1,24 @@
+---
+title: "Authentication"
+description: "Learn how to set up authentication in your MakerKit application."
+publishedAt: 2024-04-11
+order: 1
+---
+
+MakerKit uses Supabase to manage authentication within your application.
+
+By default, every kit comes with the following built-in authentication methods:
+- **Email/Password** - we added, by default, the traditional way of signing in
+- **Third Party Providers** - we also added by default Google Auth sign-in
+- **Email Links**
+- **Phone Number**
+
+You're free to add (or remove) any of the methods supported by Supabase's
+Authentication: we will see how.
+
+This documentation will help you with the following:
+ - **Setup** - setting up your Supabase project
+ - **SSR** - use SSR to persist your users' authentication, adding new
+providers
+ - **Customization** - an overview of how MakerKit works so that you can adapt
+it to your own application's needs