docs: add mention to use composer require inside container

Author: maxhelias

docs/extra-services.md

@@ -8,5 +8,11 @@ The currently supported packages are:
 * `symfony/orm-pack`: install a PostgreSQL service
 * `symfony/mercure-bundle`: use the Mercure.rocks module shipped with Caddy
 * `symfony/panther`: install chromium and these drivers
-* `symfony/mailer`: install a MailCatcher service
+* `symfony/mailer`: install a Mailpit service
 * `blackfireio/blackfire-symfony-meta`: install a Blackfire service
+
+> [!NOTE]
+> If a recipe modifies the Dockerfile, the container needs to be rebuilt.
+
+> [!WARNING]
+> We recommend that you use the `composer require` command inside the container in development mode so that recipes can be applied correctly