solaoi

I've found that some models do not have `model.encoder.embedded_positions.weight` in the conversion logs. The default model (i.e. OPUS-MT-EN-ROMANCE) has the following conversion logs. ``` converted model.encoder.embed_positions.weight - 128 bytes converted...

I added two parameters ( `model.encoder.embed_positions.weight`, `model.decoder.embed_positions.weight`) as below. This solved the problem. But the translation quality is too stupid, so how to convert is something wrong. ``` // add...

I think maybe the num_beams in config.json is not properly handled. MarianConfig and BertConfig are equivalent as follows. https://github.com/guillaume-be/rust-bert/blob/c37eb32857edb4de0b76066c39b5de52ac7db7dd/src/marian/marian_model.rs#L524 BertConfig has no num_beams. https://github.com/guillaume-be/rust-bert/blob/c37eb32857edb4de0b76066c39b5de52ac7db7dd/src/bert/bert_model.rs#L141-L158