Update the documentation of jQuery.data to indicate what the function actually accepts for the 1st parameter.

The documentation for jQuery.data gives the following signatures:

jQuery.data( element, key, value )
jQuery.data( element, key )
jQuery.data( element )

In all three the element parameter is typed as Element. However, jQuery does accept an element which is of type Document. Two pieces of evidence:

1. In practice, I've used jQuery.data on Document objects for years, without any trouble.

2. The data machinery calls on acceptData to detect whether a node is fit to be used as the first argument of the data function. acceptData's code and comments both explicitly consider that Document is a valid node.

It seems that JavaScript objects that do not have a numeric nodeType field can also be used with jQuery.data. I'm mentioning this for completeness. I've never used this capability.

Start with the jQuery.data documentation page and compare its parameter signatures with src/data/var/acceptData.js, which the issue identifies as evidence for supported nodes. Update the documentation so the first parameter accurately reflects the accepted Document type and clarify the mentioned object behavior if confirmed. Done means the published signatures match the supported inputs.