Recognize background-color style in wxHtmlWindow.

Just treat it as a synonym for "background" i.e. the same as HTML3 BGCOLOR.

Closes #13173.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70121 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/html/htmltag.cpp

@@ -464,6 +464,7 @@ wxHtmlTag::wxHtmlTag(wxHtmlTag *parent,
         { "width",              "WIDTH"         },
         { "vertical-align",     "VALIGN"        },
         { "background",         "BGCOLOR"       },
+        { "background-color",   "BGCOLOR"       },
     };
 
     wxHtmlStyleParams styleParams(*this);