[Docs] Model_doc structure/clarity improvements (#26876)

* first batch of structure improvements for model_docs

* second batch of structure improvements for model_docs

* more structure improvements for model_docs

* more structure improvements for model_docs

* structure improvements for cv model_docs

* more structural refactoring

* addressed feedback about image processors

docs/source/en/model_doc/encodec.md

@@ -26,6 +26,9 @@ The abstract from the paper is the following:
 
 This model was contributed by [Matthijs](https://huggingface.co/Matthijs), [Patrick Von Platen](https://huggingface.co/patrickvonplaten) and [Arthur Zucker](https://huggingface.co/ArthurZ). 
 The original code can be found [here](https://github.com/facebookresearch/encodec).
+
+## Usage example 
+
 Here is a quick example of how to encode and decode an audio using this model:
 
 ```python 
@@ -45,7 +48,6 @@ Here is a quick example of how to encode and decode an audio using this model:
 >>> audio_values = model(inputs["input_values"], inputs["padding_mask"]).audio_values
 ```
 
-
 ## EncodecConfig
 
 [[autodoc]] EncodecConfig