hOCR editor: use "scan_res" instead of "res"

[kba]

cf. https://github.com/kba/hocrjs/issues/68:

The problem is the res property which is not part of the hOCR spec. I think this should be scan_res, i.e. in https://github.com/manisandro/gImageReader/blob/8a046ec7bf64e996fbc81187306334fbd11873c9/qt/src/hocr/OutputEditorHOCR.cc#L268:

-     attrs["res"] = QString::number(pageInfos.resolution);
+ attrs["scan_res"] = QString::number(pageInfos.resolution);

ht @khashashin

[manisandro]

Thanks

[khashashin]

@kba @manisandro thank you for the fix 👍