Try out parquet and xml

[racinmat]

We claim we are able to process other tree-like data, e.g. XML or parquet. It would be good to add examples and try out if it's all working out of the box.
We have not tried it in reproducible manner yet AFAIK.

[simonmandlik]

This would be nice, but absolute majority of our datasets are JSON documents. So not a priority for now