[css-color-4] Add example of SelectedItem with SelectedItemText to Example 32 (#6949)

Author: 36degrees

css-color-4/Overview.bs

@@ -2134,6 +2134,7 @@ System Colors</h3>
 		<p>Mark with GrayText <span style="background-color:Mark; color:GrayText">GrayText</span></p>
 		<p>Highlight with HighlightText <span style="background-color:Highlight; color:HighlightText">HighlightText</span></p>
 		<p>Highlight with GrayText <span style="background-color:Highlight; color:GrayText">GrayText</span></p>
+		<p>SelectedItem with SelectedItemText <span style="background-color:SelectedItem; color:SelectedItemText">SelectedItemText</span></p>
 	</div>
 
 	Earlier versions of CSS defined additional <<system-color>>s,