* scalafix: 0.9.0 -> 0.10.0
Bump scala version 2.12.7 -> 2.13.8 (latest AFAICT), as well.
Prefer hash format that matches what nix outputs these days
for easier updating.
* scalafix: shell completion (bash, zsh)
* scalafix: use setJavaClassPath, drop jdk dep
No need to pull in entire JDK just to use the setup-hook.