WMT21 Marian translation model (ca-oc)

This is a neural machine translation model for Catalan to Occitan translation and constitutes the primary CUNI submission for [WMT21 Multilingual Low-Resource Translation for Indo-European Languages Shared Task](https://www.statmt.org/wmt21/multilingualHeritage-translation-task.html). The model is available for download from the LINDAT repository.