[css-ui-4] user-select must not apply to ::first-line/letter

Author: frivoal

css-ui-4/Overview.bs

@@ -421,6 +421,9 @@ Omitted values are set to their initial values.
 		Computed value: See below
 	</pre>
 
+	User Agents must not apply the 'user-select' property to
+	the ''::first-line'' and ''::first-letter'' pseudo elements.
+
 	The computed value is the specified value,
 	except:
 	<ol>