Add syntax xml for Hare language

I believe the KDE xml file was just added for the [Hare language](https://harelang.org/).

https://invent.kde.org/frameworks/syntax-highlighting/-/merge_requests/514
https://invent.kde.org/frameworks/syntax-highlighting/-/blob/master/data/syntax/hare.xml
https://kate-editor.org/syntax/data/syntax/hare.xml

Can this be added to skylighting so that syntax highlighting for Hare will work in Pandoc?

Start with the linked KDE hare.xml syntax definition, then inspect how skylighting stores and loads syntax definitions. Add the Hare definition so Pandoc can recognize and highlight Hare source, and verify the resulting highlighting through the project's existing checks or Pandoc usage.

Written by the indexing model from the issue text.