forward lang ids in TransformerWordEmbeddings

[helpmefindaname]

closes #2416

[alanakbik]

Hello @helpmefindaname thanks for the PR! I did not know that some transformers require language IDs to improve embeddings. Is there documentation on this somewhere, bzw a list of all transformer models that use language IDs?

[helpmefindaname]

Hey @alanakbik sure, here is the documentation: https://huggingface.co/transformers/multilingual.html#xlm-language-embeddings
it is basically a feature of XLM, there are also more models based on XLM that benefit from it, in my case it is https://huggingface.co/microsoft/unihanlm-base

[alanakbik]

@helpmefindaname thanks for adding this!