Adding missing info to tutorial

This is a very helpful tutorial! Unfortunately there are a couple things missing that would help the clarity a lot.
1. The first would be to show what your config.json file is in ./models/EsperBERTo-small.
2. It's not entirely clear to me how to integrate EsperantoDataset into run_language_modeling.py. Showing the changes required to properly load the tokenizer would be very helpful.

Thanks again!

Start with the tutorial section covering ./models/EsperBERTo-small and run_language_modeling.py, then inspect how EsperantoDataset is introduced. Document the expected config.json contents and the tokenizer-loading changes needed to integrate EsperantoDataset, using the tutorial's existing examples to verify the explanation is complete.

Written by the indexing model from the issue text.