Added a nice white color for the table-of-contents item

WHen hovering over an item in the table of contents, the default color
of text is not very visible with the #4e4a4a background color. This
fixes the issue for me.

styles/readtheorg/css/readtheorg.css

@@ -767,6 +767,7 @@ hr{
 }
 
 #table-of-contents a:hover{
+	color: #ffffff !important;
     background-color:#4e4a4a;
     cursor:pointer}