Update for recent tooling versions - Scala 3

[OndrejSpanel]

Same as #19, but using Scala 3 this time.

All steps updated to recent tooling versions using Scala 3.3.3

[gzm0]

 git range-diff 1.x~7..1.x refs/pull/20/head~7..refs/pull/20/head
1:  a8b7934 ! 1:  b0551c9 Step 1: Setup
    @@ build.sbt (new)
     +enablePlugins(ScalaJSPlugin)
     +
     +name := "Scala.js Tutorial"
    -+scalaVersion := "2.13.13"
    ++scalaVersion := "3.3.3"
     +
     +// This is an application with a main method
     +scalaJSUseMainModuleInitializer := true
2:  916f152 = 2:  019dd65 Step 2: Integrating with HTML
3:  b6470bb ! 3:  322e735 Step 3: Using the DOM
    @@ Commit message
         Step 3: Using the DOM
     
      ## build.sbt ##
    -@@ build.sbt: scalaVersion := "2.13.13"
    +@@ build.sbt: scalaVersion := "3.3.3"
      
      // This is an application with a main method
      scalaJSUseMainModuleInitializer := true
4:  ffbe911 = 4:  d2adbfe Step 4: Reacting on User Input
5:  39a4c2b = 5:  66cb9a6 Step 5: Setup the UI in Scala.js
6:  11cea4e ! 6:  ece1735 Step 6: Testing
    @@ Commit message
         Step 6: Testing
     
      ## build.sbt ##
    -@@ build.sbt: scalaVersion := "2.13.13"
    +@@ build.sbt: scalaVersion := "3.3.3"
      scalaJSUseMainModuleInitializer := true
      
      libraryDependencies += "org.scala-js" %%% "scalajs-dom" % "2.8.0"
7:  88c4bdb = 7:  65fe0b6 Step 7: Optimizing for Production

[gzm0]

@sjrd, could you take a look at this? I do not know any Scala 3. Feels to me that if we'd want to offer this, we'd also have to update the code (to quiet syntax at least?).

[sjrd]

Looks good to me. We could update to indentation-based syntax, sure, but we don't have to in a first pass.

[OndrejSpanel]

I suggest making the Scala 3 version default and archiving the Scala 2 version in the same manner all previous versions are archived (in branches). I do not think there is any reason to start a new project with Scala 2 unless you have a specific reason, the tools seem stable and reliable enough to me now (I would not say this a few months ago).