Spray json support for scala 3

[MichelEdkrantz]

Hi,
reaching out since my company is using spray json for a lot of things, and we also like your libraries :)

Wanted to check regarding spray json, and scala 3 support. Spray json also has a Scala 3 build, but not linked in your sbt build. Any historic reason for this or not doing this? It might be as easy as adding scala3 below.

If I opened a PR for this, should it be for the client3 or client4?

lazy val sprayJson = (projectMatrix in file("json/spray-json"))
  .settings(commonJvmSettings)
  .settings(
    name := "spray-json",
    libraryDependencies ++= Seq(
      "io.spray" %% "spray-json" % "1.3.6"
    ),
    scalaTest
  )
  .jvmPlatform(scalaVersions = scala2)
  .dependsOn(core, jsonCommon)

[adamw]

Probably nobody submitted a patch yet - no other reasons, if the tests pass. Can you maybe create a PR?

[kciesielski]

If I opened a PR for this, should it be for the client3 or client4?

I think it's worth adding for client3 and client4.

[MichelEdkrantz]

Added another PR here for v3 - #2186