docs: Default Scala quickstart to Scala 3, test on both 3 and 2.13 (#4405)

Author: johanandren

.github/workflows/check-samples.yml

@@ -53,7 +53,7 @@ jobs:
 
       - name: Publish artifacts locally
         run: |-
-          sbt "publishLocal; publishM2"
+          sbt "+publishLocal; publishM2"
 
       - name: Test akka-http-quickstart-java
         run: |-
@@ -63,7 +63,8 @@ jobs:
       - name: Test akka-http-quickstart-scala
         run: |-
           cd samples/akka-http-quickstart-scala
-          sbt test -Dakka-http.version=`cat ~/.version`
+          sbt "++2.13.14!; test;" -Dakka-http.version=`cat ~/.version`
+          sbt "clean; test;" -Dakka-http.version=`cat ~/.version`
 
       - name: Email on failure
         if: ${{ failure() }}

samples/akka-http-quickstart-scala/build.sbt

@@ -13,7 +13,7 @@ lazy val root = (project in file(".")).
   settings(
     inThisBuild(List(
       organization    := "com.example",
-      scalaVersion    := "2.13.14"
+      scalaVersion    := "3.3.3"
     )),
     name := "akka-http-quickstart",
     libraryDependencies ++= Seq(