Publish Dotty builds

[ashawley]

I've added logic for Dotty to the build script in #387.

There should be two Sonatype repos with Dotty builds, one for 0.20-RC1 and one for 0.21-RC1.

[lrytz]

Here are the staging repos:

• https://oss.sonatype.org/content/repositories/orgscala-lang-2041/
• https://oss.sonatype.org/content/repositories/orgscala-lang-2039/

Let me know if they should be released.

[ashawley]

A smoke test suggests they work:

https://github.com/ashawley/dotty-scala-xml-example

[ashawley]

They look good to me. Could you release?

[SethTisue]

I hit "release" in the web UI

[ashawley]

Thanks!