doc: add a smooth scrolling effect to the sidebar

PR-URL: #59007
Reviewed-By: Aviv Keller <me@aviv.sh>

Author: btea

doc/api_assets/api.js

@@ -197,7 +197,7 @@
 
     if (!link) return;
 
-    link.scrollIntoView({ block: 'center' });
+    link.scrollIntoView({ behavior: 'smooth', block: 'center' });
   }