Adds a reference to the middleware overview.

docs/content/providers/docker.md

@@ -182,7 +182,7 @@ This option can be overridden on a container basis with the `traefik.docker.netw
 
 ### `defaultRule`
 
-_Optional, Default=Host(`{{ normalize .Name }}`)_
+_Optional, Default=```Host(`{{ normalize .Name }}`)```_
 
 For a given container if no routing rule was defined by a label, it is defined by this defaultRule instead.
 It must be a valid [Go template](https://golang.org/pkg/text/template/),
@@ -190,8 +190,15 @@ augmented with the [sprig template functions](http://masterminds.github.io/sprig
 The container service name can be accessed as the `Name` identifier,
 and the template has access to all the labels defined on this container.
 
-```toml
-defaultRule = "Host(`{{ .Name }}.{{ index .Labels \"customLabel\"}}`)"
+```toml tab="File"
+[docker]
+defaultRule = ""
+# ...
+```
+
+```txt tab="CLI"
+--providers.docker
+--providers.docker.defaultRule="Host(`{{ .Name }}.{{ index .Labels \"customLabel\"}}`)"
 ```
 
 ### `swarmMode`
@@ -246,6 +253,8 @@ You can declare pieces of middleware using labels starting with `traefik.http.mi
 
     If you declare multiple middleware with the same name but with different parameters, the middleware fails to be declared.
 
+More information about available middlewares in the dedicated [middlewares section](../middlewares/overview.md).
+
 ### TCP
 
 You can declare TCP Routers and/or Services using labels.