Prog8 syntax highlighting file for IntelliJ IDEA and Jetbrains Rider.

Copy the file Prog8.xml to your IDEA/Rider filetypes folder.
If this folder doesn't yet exist, simply create it.
After installing this file, restart the IDEA.

The exact location of the folder varies per operating system and
IDE version, but for me it is currently this on Linux:

  $HOME/.config/JetBrains/IntelliJIdea2021.3/filetypes/

