add healthcheck notice

faq/serverless-containers.mdx

@@ -98,4 +98,9 @@ Protocol switching is currently not available in the console but can be changed
 
 ## Why does my gRPC container not respond?
 
-Containers use http1 by default, yet the gRPC protocol requires http2. You can upgrade the protocol to http2 (`h2c`).
+Containers use http1 by default, yet the gRPC protocol requires http2. You can upgrade the protocol to http2 (`h2c`).
+
+## How does Serverless Container healthcheck work ?
+
+A Serverless Container is set to `ready` once the specified port is correctly bound to the container, and will start receiving traffic. If your application needs to perform some tasks before receiving traffic (e.g. connect to a DB), it's important to run them before binding to the port (starting the webserver).
+For now, the `HEALTHCHECK` Docker directive has no impact on container readiness. In the future, the healthcheck will be customizable for your applications.