DocLint: check for HTML start element at end of body

A common error that is detected by HTML checkers (like htmltidy) is an empty paragraph between the description for an element and the beginning of the section containing the block tags. The most common form of this is a trailing "<p>" at the end of the main description.

DocLint could specifically detect this case and give an error if it is detected. The error would most likely be best in the HTML category of errors.