build with sbt 2.x

[raboof]

Depends on cross-builds for:

• sbt-paradox-theme
• sbt-site-paradox
• sbt-twirl https://repo1.maven.org/maven2/org/playframework/twirl/sbt-twirl_sbt2_3/
• sbt-pekko-build
• sbt-source-dist
• sbt-reproducible-builds feat: cross-build for sbt 2.x raboof/sbt-reproducible-builds#451

[mkurz]

• sbt-twirl

https://repo1.maven.org/maven2/org/playframework/twirl/sbt-twirl_sbt2_3/