Add allowEmptyServices for Docker provider

docs/content/providers/docker.md

@@ -714,3 +714,30 @@ providers:
 ```bash tab="CLI"
 --providers.docker.tls.insecureSkipVerify=true
 ```
+
+### `allowEmptyServices`
+
+_Optional, Default=false_
+
+If the parameter is set to `true`,
+any [servers load balancer](../routing/services/index.md#servers-load-balancer) defined for Docker containers is created 
+regardless of the [healthiness](https://docs.docker.com/engine/reference/builder/#healthcheck) of the corresponding containers.
+It also then stays alive and responsive even at times when it becomes empty,
+i.e. when all its children containers become unhealthy.
+This results in `503` HTTP responses instead of `404` ones,
+in the above cases.
+
+```yaml tab="File (YAML)"
+providers:
+  docker:
+    allowEmptyServices: true
+```
+
+```toml tab="File (TOML)"
+[providers.docker]
+  allowEmptyServices = true
+```
+
+```bash tab="CLI"
+--providers.docker.allowEmptyServices=true
+```