Update sbt-scalajs, scalajs-compiler, ... to 1.20.1 (#498)

Co-authored-by: Darren Gibson <zarthross@users.noreply.github.com>

Author: scala-steward

project/plugins.sbt

@@ -1,4 +1,4 @@
 addSbtPlugin("io.circe" % "sbt-circe-org" % "0.4.8")
 addSbtPlugin("org.scala-native" % "sbt-scala-native" % "0.5.9")
-addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.19.0")
+addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.20.1")
 addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.14.4")