[feature request] workflow_lint could use a structured data output

Apparently it supports XSD but I cannot reproduce this

```
(.venv) 12:21:43|(smorg) [user@w-galaxy:~/arbeit/galaxy/training-material]1$ planemo workflow_lint topics/variant-analysis/tutorials/dunovo/workflows/dunovo.ga --report_xunit out.xml
...
(.venv) 12:21:41|(smorg) [user@w-galaxy:~/arbeit/galaxy/training-material]1$ cat out.xml
cat: out.xml: No such file or directory
```

but if there's an option for maybe, json output? That'd be really useful.

Additionally if there is any possibility for emitting line numbers, that would be truly incredible and I can generate much nicer output with reviewdog for our users.