Add jdk versions 18-21

[jborgers]

I see only GraalVm has 18+ versions. Please add for the other distributions, too.

[paulkre]

Any workarounds?

[stephankoelle]

use the correct fork: https://github.com/Jabba-Team/jabba

[RohimChou]

Can set the JABBA_INDEX environment variable to point to a custom or community-maintained index:

# PowerShell
$env:JABBA_INDEX = "https://github.com/typelevel/jdk-index/raw/main/index.json"

# Bash
export JABBA_INDEX="https://github.com/typelevel/jdk-index/raw/main/index.json"

see: https://github.com/typelevel/jdk-index