Add example for multiple service per container

docs/content/routing/providers/docker.md

@@ -58,6 +58,26 @@ Attach labels to your containers and let Traefik do the rest!
         Setting the label `traefik.http.services.xxx.loadbalancer.server.port`
         overrides that behavior.
 
+??? example "Specifying more than one router and service per container"
+
+    Forwarding requests to more than one port on a container requires referencing the service loadbalancer port definition using the service parameter on the router.
+
+    In this example, requests are forwarded for `http://example-a.com` to `http://<private IP of container>:8000` in addition to `http://example-b.com` forwarding to `http://<private IP of container>:9000`:
+
+    ```yaml
+    version: "3"
+    services:
+      my-container:
+        # ...
+        labels:
+          - traefik.http.routers.www-router.rule=Host(`example-a.com`)
+          - traefik.http.routers.www-router.service=www-service
+          - traefik.http.services.www-service.loadbalancer.server.port=8000
+          - traefik.http.routers.admin-router.rule=Host(`example-b.com`)
+          - traefik.http.routers.admin-router.service=admin-service
+          - traefik.http.services.admin-service.loadbalancer.server.port=9000
+    ```
+
 ??? example "Configuring Docker Swarm & Deploying / Exposing Services"
 
     Enabling the docker provider (Swarm Mode)