Merge pull request cquiroz#420 from scala-steward/update/sbt-scalajs-1.12.0

Update sbt-scalajs, scalajs-compiler, ... to 1.12.0

Author: cquiroz

project/plugins.sbt

@@ -1,6 +1,6 @@
 addSbtPlugin("org.portable-scala" % "sbt-crossproject" % "1.2.0")
 
-addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.11.0")
+addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.12.0")
 
 addSbtPlugin("io.github.cquiroz" % "sbt-tzdb" % "4.1.0")