Update sbt-scalajs, scalajs-compiler, ... to 1.20.1

Author: scala-steward

project/plugins.sbt

@@ -1,5 +1,5 @@
 // scala-js
-addSbtPlugin("org.scala-js"                % "sbt-scalajs"              % "1.18.2")
+addSbtPlugin("org.scala-js"                % "sbt-scalajs"              % "1.20.1")
 addSbtPlugin("ch.epfl.scala"               % "sbt-scalajs-bundler"      % "0.21.1")
 addSbtPlugin("org.portable-scala"          % "sbt-scalajs-crossproject" % "1.3.2")
 addSbtPlugin("org.scalablytyped.converter" % "sbt-converter"            % "1.0.0-beta44")