docs: add styled callout for References & Links with external links opening in new tab

Author: barissayli

docs/assets/css/custom.css

@@ -5,4 +5,19 @@
     line-height: 1.3 !important;
     text-align: center !important;
     padding: 0.5rem !important;
+}
+
+.callout {
+    border-left: 4px solid #0ea5e9; /* cyan */
+    background: #f8fafc;            /* very light slate */
+    padding: 0.85rem 1rem;
+    margin: 1.25rem 0;
+    border-radius: 8px;
+}
+.callout .title {
+    font-weight: 700;
+    margin-bottom: 0.35rem;
+}
+.callout.learn-more {
+    border-left-color: #2563eb; /* blue-600 */
 }

docs/index.md

@@ -81,5 +81,10 @@ Generated wrappers can be found under:
 
 ## 📂 References & Links
 
-- 🌐 [GitHub Repository](https://github.com/bsayli/spring-boot-openapi-generics-clients)
-- 📘 [Medium Article — Type-Safe Generic API Responses](https://medium.com/@baris.sayli/type-safe-generic-api-responses-with-spring-boot-3-4-openapi-generator-and-custom-templates-ccd93405fb04)  
+<div class="callout learn-more">
+  <div class="title">🔗 References & Links</div>
+  <ul>
+    <li>🌐 <a href="https://github.com/bsayli/spring-boot-openapi-generics-clients" target="_blank" rel="noopener">GitHub Repository</a></li>
+    <li>📘 <a href="https://medium.com/@baris.sayli/type-safe-generic-api-responses-with-spring-boot-3-4-openapi-generator-and-custom-templates-ccd93405fb04" target="_blank" rel="noopener">Medium Article — Type-Safe Generic API Responses</a></li>
+  </ul>
+</div>