Describe "exposed_port" Config for Healthcheck

_docs/configuration.md

@@ -693,6 +693,17 @@ The HTTP health checks assume that the `curl` command is available inside the co
 
 When starting container healthcheck by default will only show last 50 lines. That might be not enough when something goes wrong - so you can add `log_lines` params and specify larger number if required.
 
+## Using a custom port for the healthcheck with multiple apps
+
+Healthcheck is binding containers port to server's port. When running multiple applications on the same server and deploying them in parallel you should specify different port for each application.
+
+```yaml
+healthcheck:
+  exposed_port: 4000 # 3999 is the default one
+```
+
+This allows you to run multiple applications on the same server sharing the same Traefik instance and port
+
 ## Using rolling deployments
 
 When deploying to large numbers of hosts, you might prefer not to restart your services on every host at the same time.