Support for Java things

[jmfayard]

Java is amazingly hard to install on MacOS.

Would it be possible to add support for https://sdkman.io ?

In config.js, I would like to list which java things I want to install.
For example

module.exports = {
  sdkman: {
     java: "13.0.0.j9-adpt",
     gradle: "5.6.3",
     kotlin: "1.3.50",
     kscript: "2.8.0"
  }
}