docs: marshmallow fixes
.. _marshmallow:
-Marshmallow v3 compatibility
-============================
+Marshmallow v2/v3 compatibility
+===============================
Marshmallow
-----------
-Marhsmallow is a package for serialization and deserialization of complex data
+Marshmallow is a package for serialization and deserialization of complex data
structures from and to Python types. You can discover its usage within
Invenio in the `documentation <https://invenio.readthedocs.io/en/latest/tutorials/understanding-data-models.html?highlight=marshmallow#define-a-marshmallow-schema>`_.
