[doc] How to plug Tapir into existing Play app

generated-doc/out/server/play.md

@@ -4,7 +4,7 @@ To expose endpoint as a [play-server](https://www.playframework.com/) first add
 ```scala
 "com.softwaremill.sttp.tapir" %% "tapir-play-server" % "0.16.16"
 ```
-and 
+and (if you don't already depends on Play)
 ```scala
 "com.typesafe.play" %% "play-akka-http-server" % "2.8.2"
 ```
@@ -71,6 +71,10 @@ val anEndpoint: Endpoint[(String, Int), Unit, String, Nothing] = ???
 val aRoute: Routes = anEndpoint.toRoute((logic _).tupled)
 ```
 
+## Bind the routes
+
+### Creating the HTTP server manually
+
 An HTTP server can then be started as in the following example:
 
 ```scala
@@ -92,6 +96,27 @@ object Main {
 }
 ```
 
+### As part of an existing Play application
+
+Or, if you already have an existing Play application, you can create a `Router` class and bind it to the application.
+
+First, add a line like following in the `routes` files:
+```
+->      /api                        api.ApiRouter
+```
+Then create a class like this:
+```scala
+class ApiRouter @Inject() () extends SimpleRouter {
+  override def routes: Routes = {
+    // Routes generated by Tapir (see above)
+    aRoute
+      .orElse(anotherRoute)
+  }
+}
+```
+
+Find more details about how to bind a `Router` to your application in the [Play framework documentation](https://www.playframework.com/documentation/2.8.x/ScalaSirdRouter#Binding-sird-Router).
+
 ## Configuration
 
 The interpreter can be configured by providing an implicit `PlayServerOptions` value and status mappers, see