[Docs] Improve docs for MMS loading of other languages (#24292)

* Improve docs

* Apply suggestions from code review

* upload readme

* Apply suggestions from code review

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

---------

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

docs/source/en/model_doc/mms.mdx

@@ -44,11 +44,51 @@ MMS's architecture is based on the Wav2Vec2 model, so one can refer to [Wav2Vec2
 
 The original code can be found [here](https://github.com/facebookresearch/fairseq/tree/main/examples/mms).
 
+## Loading
+
+By default MMS loads adapter weights for English. If you want to load adapter weights of another language 
+make sure to specify `target_lang=<your-chosen-target-lang>` as well as `"ignore_mismatched_sizes=True`.
+The `ignore_mismatched_sizes=True` keyword has to be passed to allow the language model head to be resized according
+to the vocabulary of the specified language.
+Similarly, the processor should be loaded with the same target language
+
+```py
+from transformers import Wav2Vec2ForCTC, AutoProcessor
+
+model_id = "facebook/mms-1b-all"
+target_lang = "fra"
+
+processor = AutoProcessor.from_pretrained(model_id, target_lang=target_lang)
+model = Wav2Vec2ForCTC.from_pretrained(model_id, target_lang=target_lang, ignore_mismatched_sizes=True)
+```
+
+<Tip>
+
+You can safely ignore a warning such as:
+
+```text
+Some weights of Wav2Vec2ForCTC were not initialized from the model checkpoint at facebook/mms-1b-all and are newly initialized because the shapes did not match:
+- lm_head.bias: found shape torch.Size([154]) in the checkpoint and torch.Size([314]) in the model instantiated
+- lm_head.weight: found shape torch.Size([154, 1280]) in the checkpoint and torch.Size([314, 1280]) in the model instantiated
+You should probably TRAIN this model on a down-stream task to be able to use it for predictions and inference.
+```
+
+</Tip>
+
+If you want to use the ASR pipeline, you can load your chosen target language as such:
+
+```py
+from transformers import pipeline
+
+model_id = "facebook/mms-1b-all"
+target_lang = "fra"
+
+pipe = pipeline(model=model_id, model_kwargs={"target_lang": "fra", "ignore_mismatched_sizes": True})
+```
+
 ## Inference
 
-By default MMS loads adapter weights for English, but those can be easily switched out for another language.
+Next, let's look at how we can run MMS in inference and change adapter layers after having called [`~PretrainedModel.from_pretrained`]
-Let's look at an example.
-
 First, we load audio data in different languages using the [Datasets](https://github.com/huggingface/datasets).
 
 ```py