docs(sdb): add links to supported extension doc MTA-5139 (scaleway#3820)

* docs(sdb): add links to supported extension doc MTA-5139

* docs(sdb): update

Author: SamyOubouaziz

faq/serverless-sql-databases.mdx

@@ -53,4 +53,8 @@ You can avoid cold starts by provisioning a minimum of 1 vCPU or more.
 The following features are currently not supported and will be implemented at a later time:
 
   - Manual backups (you can still perform manual backups using SQL queries or via SQL administration tools such as pgAdmin)
-  - Several SQL commands detailed in the [Known differences with default PostgreSQL](/serverless/sql-databases/reference-content/known-differences/) documentation
+  - Several SQL commands detailed in the [Known differences with default PostgreSQL](/serverless/sql-databases/reference-content/known-differences/) documentation
+
+## Which PostgreSQL extensions are available?
+
+Refer to our dedicated [PostgreSQL extentions reference page](/serverless/sql-databases/reference-content/supported-postgresql-extensions/) for a list of all available extensions and more details about each one.

serverless/sql-databases/reference-content/known-differences.mdx

@@ -17,14 +17,11 @@ Serverless SQL Database is based on PostgreSQL engine and thus provides standard
 
 If you require strict compatibility with all PostgreSQL features, you can use [Managed Databases for PostgreSQL](/managed-databases/postgresql-and-mysql/quickstart/) instead.
 
-## Unsupported SQL features
+## Unsupported PostgreSQL extensions
 
-- Installing extensions is not yet supported. We plan to support extensions similar to [Managed Databases for PostgreSQL available extensions](https://www.scaleway.com/en/docs/faq/databases-for-postgresql-and-mysql/#which-postgresql-extensions-are-available) in future releases.
+Serverless SQL Databases support the most popular PostgreSQL extensions. Refer to the [dedicated documentation](/serverless/sql-databases/reference-content/supported-postgresql-extensions/) for more information. 
 
-    ```sql
-    CREATE EXTENSION extension_name;
-    NOTIFY channel, 'message';
-    ```
+## Unsupported SQL features
 
 - Notifying and listening channels using the `NOTIFY` and `LISTEN` commands can be performed, but message delivery is not guaranteed.