Update sbt-scalajs, ... to 1.6.0

Author: scala-steward

Diff for: .travis.yml

@@ -13,7 +13,7 @@ scala:
 
 env:
   - ADOPTOPENJDK=8     SCALAJS_VERSION=       CACHE_WORKAROUND=see-PR-335
-  - ADOPTOPENJDK=8     SCALAJS_VERSION=1.5.1  CACHE_WORKAROUND=see-PR-335
+  - ADOPTOPENJDK=8     SCALAJS_VERSION=1.6.0  CACHE_WORKAROUND=see-PR-335
   - ADOPTOPENJDK=11    SCALAJS_VERSION=       CACHE_WORKAROUND=see-PR-335
 
 matrix:

Diff for: project/plugins.sbt

@@ -1,5 +1,5 @@
 val scalaJSVersion =
-  Option(System.getenv("SCALAJS_VERSION")).filter(_.nonEmpty).getOrElse("1.5.1")
+  Option(System.getenv("SCALAJS_VERSION")).filter(_.nonEmpty).getOrElse("1.6.0")
 
 val scalaNativeVersion =
   Option(System.getenv("SCALANATIVE_VERSION")).filter(_.nonEmpty).getOrElse("0.4.0")