$output: $wgOut
$term: Search term specified by the user
+'SpecialSearchResultsAppend': Called immediately before returning HTML
+on the search results page. Useful for including a feedback link.
+$specialSearch: SpecialSearch object ($this)
+$output: $wgOut
+
'SpecialSearchSetupEngine': Allows passing custom data to search engine.
$search: SpecialSearch special page object
$profile: String: current search profile