Update README.md

Hi,

Many thanks for extending mHuBERT-147 for Breton! My many French colleagues were super hyped about it! :)
I'm doing this PR to request the addition of "base_model: utter-project/mHuBERT-147" on your readme header, so that your fine-tuned model is advertised as "finetunes" of mHuBERT-147 (see here https://huggingface.co/models?other=base_model:finetune:utter-project/mHuBERT-147).

All the best,

README.md

@@ -22,6 +22,7 @@ language:
 - br
 metrics:
 - wer
+base_model: utter-project/mHuBERT-147
 pipeline_tag: automatic-speech-recognition
 datasets:
 - mozilla-foundation/common_voice_15_0