deps: update all sorts of stuff (com-lihaoyi#121)

This pr goes through and makes the various updates:
  - Bumps mill to the latest 0.10.5
  - Bumps to the latest Scala versions for 2 and latest 3.1.x version
  - Drops 0.x support for ScalaJS
  - Move Scala native to 0.4.x
  - Adds in dependabot
  - Starts to cross test on 8 and 17
  - Updates checkout and java actions

Support Scala Native - Scala 3 (com-lihaoyi#119)

* Support Scala Native - Scala 3

- Update Mill to 10.0.0

* Skip docJar in Scala 3 Scala Native

Merge pull request com-lihaoyi#114 from com-lihaoyi/version-0.2.7

Version 0.2.7

Merge pull request com-lihaoyi#107 from com-lihaoyi/fix-sonatype-publ…

…ishing

Fix Sonatype publishing

Merge pull request com-lihaoyi#99 from lolgab/bump-version-0.2.3

Bump version to 0.2.3