Merge pull request #291 from scala-steward/update/sbt-scalajs-1.9.0

Update sbt-scalajs, scalajs-library_2.13, ... to 1.9.0

Author: EmergentOrder

project/plugins.sbt

@@ -1,6 +1,6 @@
 addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject"      % "1.1.0")
 addSbtPlugin("org.portable-scala" % "sbt-scala-native-crossproject" % "1.1.0")
-addSbtPlugin("org.scala-js"       % "sbt-scalajs"                   % "1.8.0")
+addSbtPlugin("org.scala-js"       % "sbt-scalajs"                   % "1.9.0")
 addSbtPlugin("org.scala-native"   % "sbt-scala-native"              % "0.4.3")
 addSbtPlugin("ch.epfl.scala"      % "sbt-scalafix"                  % "0.9.34")
 addSbtPlugin("org.scalameta"      % "sbt-scalafmt"                  % "2.4.6")