Update sbt-scalajs to 0.6.28

Author: scala-steward

.travis.yml

@@ -19,7 +19,7 @@ env:
   matrix:
     # The empty SCALAJS_VERSION will only compile for the JVM
     - SCALAJS_VERSION=
-    - SCALAJS_VERSION=0.6.27
+    - SCALAJS_VERSION=0.6.28
     - SCALAJS_VERSION=1.0.0-M7
 
 matrix:

project/plugins.sbt

@@ -1,7 +1,7 @@
 addSbtPlugin("org.scala-lang.modules" % "sbt-scala-module" % "2.0.0")
 
 val scalaJSVersion =
-  Option(System.getenv("SCALAJS_VERSION")).filter(_.nonEmpty).getOrElse("0.6.27")
+  Option(System.getenv("SCALAJS_VERSION")).filter(_.nonEmpty).getOrElse("0.6.28")
 
 addSbtPlugin("org.scala-js" % "sbt-scalajs" % scalaJSVersion)