Add Spanish translation of serialization.mdx (#20245)

* Update _toctree and clone original content

* Translate first three sections

* Add more translated chapters. Only 3 more left.

* Finish translation

* Run style from doc-builder

* Address recommended changes from reviewer

docs/source/es/_toctree.yml

@@ -47,6 +47,8 @@
     title: Modelos multilingües para inferencia
   - local: converting_tensorflow_models
     title: Convertir checkpoints de TensorFlow
+  - local: serialization
+    title: Serialización
   title: Guías prácticas
 - sections:
   - local: philosophy