Update sbt-scalajs to 0.6.28

[scala-steward]

Updates org.scala-js:sbt-scalajs from 0.6.27 to 0.6.28.

I'll automatically update this PR to resolve conflicts as long as you don't change it yourself.

If you'd like to skip this version, you can just close this PR. If you have any feedback, just mention @scala-steward in the comments below.

Have a nice day!

Ignore future updates

Add this to your .scala-steward.conf file to ignore future updates of this dependency:

updates.ignore = [{ groupId = "org.scala-js", artifactId = "sbt-scalajs" }]

labels: semver-patch

[SethTisue]

I think Travis no longer obeys oraclejdk8 and we need to switch to openjdk8?

[NthPortal]

the Scala 2.13.0-RC1/scala-js 0.6.28 parts of the build matrix are failing. not sure if we need to bump to RC2, skip that part of the matrix, or something else

[Philippus]

if we set dist: trusty we can still use oraclejdk8 for a while, see ae2d4a3

[NthPortal]

@Philippus is there an advantage to that?

[sjrd]

the Scala 2.13.0-RC1/scala-js 0.6.28 parts of the build matrix are failing.

You should bump to RC2 before upgrading to Scala.js 0.6.28, yes.