Release 4.2.0

Updates for Reactive synchronize support

Merge pull request #190 from outr/update/scala-library-2.13.18

Merge pull request #191 from outr/update/scala-library-2.12.21

Merge pull request #193 from outr/update/sbt-scalajs-1.20.2

Merge pull request #195 from outr/update/sbt-scoverage-2.4.4

Merge pull request #196 from outr/update/auxlib-0.5.10

Merge pull request #198 from outr/update/sbt-1.12.2

Update sbt, scripted-plugin to 1.12.2

Update auxlib, clib, javalib, nativelib, ... to 0.5.10

Update sbt-scoverage to 2.4.4

Update sbt-scalajs, scalajs-compiler, ... to 1.20.2

Update scala-library to 2.12.21

Update scala-library to 2.13.18

CI updates