Update sbt-scalajs-crossproject to 1.2.0 (#334)

Author: scala-steward

project/plugins.sbt

@@ -1,6 +1,6 @@
 addSbtPlugin("com.geirsson" % "sbt-ci-release" % "1.5.7")
 addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.9.1")
 addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.5.1")
-addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "1.0.0")
+addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "1.2.0")
 addSbtPlugin("org.scala-js" % "sbt-jsdependencies" % "1.0.2")
 addSbtPlugin("io.get-coursier" % "sbt-shading" % "2.0.1")