Add support for sbt 2

[mkurz]

See

• [2.x] Migration plan of key plugins sbt/sbt#7698
• sbt 2.x plugin migration wiki page with list of progress
• Add support for sbt 2 playframework#12897

We can't really do much at this point but to wait for other plugins to be released first that twirl depends on:

• ch.epfl.scala:sbt-bloop_sbt2.0.0-M2_3
• com.eed3si9n:sbt-buildinfo_sbt2.0.0-M2_3
• com.github.sbt:sbt-maven-plugin_sbt2.0.0-M2_3
• com.typesafe:sbt-mima-plugin_sbt2.0.0-M2_3
• org.scala-js:sbt-scalajs_sbt2.0.0-M2_3
• org.portable-scala:sbt-scalajs-crossproject_sbt2.0.0-M2_3
• com.lightbend.sbt:sbt-java-formatter_sbt2.0.0-M2_3
• de.heikoseeberger:sbt-header_sbt2.0.0-M2_3
• com.github.sbt:sbt-ci-release_sbt2.0.0-M2_3
• org.scalameta:sbt-scalafmt_sbt2.0.0-M2_3

[mkurz]

Hmm.. seems I was too fast. We can of course already cross publish the twirl plugin with Scala 3/sbt 2, even if running sbt 1 with missing sbt 2 plugins:
https://www.scala-sbt.org/2.x/docs/en/changes/migrating-from-sbt-1.x.html#cross-building-sbt-plugin-with-sbt-1x

Makes total sense.

• See add sbt 2.x build setting #840