Add doc for serialization/deserialization of torchao optimized models

Summary:
Addressing following questions:

1. What happens if I save a quantized model
2. What happens if I load a quantized model and describing deteails like assign=True

Specifically
1. Do you need ao as a dependency when you're loading a quantized model
2. Is the saved quantized model smaller on disk than the unquantized one

Test Plan:
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Reviewers:

Subscribers:

Tasks:

Tags:

docs/source/index.rst

@@ -78,6 +78,7 @@ with more content coming soon.
       quantization
       sparsity
       performant_kernels
+      serialization
 
    .. toctree::
       :glob: