docs: add HOSTNAME docs

docs/jackson/deploy/env-variables.md

@@ -10,6 +10,13 @@ The env vars are only applicable to the Jackson service. If you are using the np
 
 ## General configuration
 
+### **HOSTNAME**
+
+The container network that the service starts listening on. 
+
+If you are planning to use Docker health check like `wget -q --spider http://localhost:{PORT}/api/health || exit 1` you will need to set `HOSTNAME=0.0.0.0` to be able to reach the service on localhost.
+Check [NextJS Standalone Good to know](https://nextjs.org/docs/pages/api-reference/next-config-js/output#automatically-copying-traced-files)
+
 ### **HOST_URL**
 
 The URL to bind to.