Mention server backend in the README

Author: mkurz

play-java-grpc-example/README.md

@@ -6,6 +6,11 @@ This is an example application that shows how to use Pekko gRPC to both expose a
 
 For detailed documentation refer to https://www.playframework.com/documentation/latest/Home and https://pekko.apache.org/docs/pekko-grpc/current/.
 
+## Server backend
+
+By default, the project uses the Akka HTTP Server backend. To switch to the Netty Server backend, enable the `PlayNettyServer` sbt plugin in the `build.sbt` file.
+In the `build.sbt` of this project, you'll find a commented line for this setting; simply uncomment it to make the switch.
+For more detailed information, refer to the Play Framework [documentation](https://www.playframework.com/documentation/3.0.x/Server).
 
 ## Sample license
 

play-scala-grpc-example/README.md

@@ -6,6 +6,11 @@ This is an example application that shows how to use Pekko gRPC to both expose a
 
 For detailed documentation refer to https://www.playframework.com/documentation/latest/Home and https://pekko.apache.org/docs/pekko-grpc/current/.
 
+## Server backend
+
+By default, the project uses the Akka HTTP Server backend. To switch to the Netty Server backend, enable the `PlayNettyServer` sbt plugin in the `build.sbt` file.
+In the `build.sbt` of this project, you'll find a commented line for this setting; simply uncomment it to make the switch.
+For more detailed information, refer to the Play Framework [documentation](https://www.playframework.com/documentation/3.0.x/Server).
 
 ## Sample license
 

play-scala-tls-example/README.md

@@ -8,6 +8,12 @@ You must have JDK 11 installed on your machine to run this, to take advantage of
 
 * [Adoptium OpenJDK](https://adoptium.net/)
 
+## Server backend
+
+By default, the project uses the Akka HTTP Server backend. To switch to the Netty Server backend, enable the `PlayNettyServer` sbt plugin in the `build.sbt` file.
+In the `build.sbt` of this project, you'll find a commented line for this setting; simply uncomment it to make the switch.
+For more detailed information, refer to the Play Framework [documentation](https://www.playframework.com/documentation/3.0.x/Server).
+
 ## Generate Certificates
 
 To use HTTPS, you must have X.509 certificates.  Generating certificates can be painful, so all the scripts needed to generate the certificates needed are included in the `scripts` directory.  For more detail, you can see the [Certificate Generation](https://www.playframework.com/documentation/latest/CertificateGeneration) section in Play WS SSL.