Fixed #9471 - Expanded ModelAdmin.raw_id_fields docs; thanks adroffne for the suggestion.

        class ArticleAdmin(admin.ModelAdmin):

            raw_id_fields = ("newspaper",)

    The ``raw_id_fields`` ``Input`` widget should contain a primary key if the

    field is a ``ForeignKey`` or a comma separated list of values if the field

    is a ``ManyToManyField``.  The ``raw_id_fields`` widget shows a magnifying

    glass button next to the field which allows users to search for and select

    a value:

    .. image:: _images/raw_id_fields.png

.. attribute:: ModelAdmin.readonly_fields

    By default the admin shows all fields as editable. Any fields in this