📝 Add link in sql-databases.md tutorial to async-sql-databases.md in advanced section. (#1813)

* Add link in sql-databases.md tutorial section to async-sql-databases.md in advanced section.

* 🎨 Update note format

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

docs/en/docs/tutorial/sql-databases.md

@@ -539,6 +539,9 @@ def read_user(user_id: int, db: Session = Depends(get_db)):
     ...
 ```
 
+!!! info
+    If you need to connect to your relational database asynchronously, see [Async SQL (Relational) Databases](../advanced/async-sql-databases.md){.internal-link target=_blank}.
+
 !!! note "Very Technical Details"
     If you are curious and have a deep technical knowledge, you can check the very technical details of how this `async def` vs `def` is handled in the [Async](../async.md#very-technical-details){.internal-link target=_blank} docs.