[css-2020] Use full title of css-easing for consistency

Author: frivoal

css-2020/Overview.bs

@@ -275,7 +275,7 @@ Background: The W3C Process and CSS</h3>
 			  [[CSS3-TRANSITIONS]]
 			  and <a href="https://www.w3.org/TR/css3-animations/">CSS Animations Level 1</a>
 			  [[CSS3-ANIMATIONS]],
-			  together with [[CSS-EASING-1]].
+			  together with <a href="https://www.w3.org/TR/css-easing-1/">CSS Easing Functions Level 1</a> [[CSS-EASING-1]].
 			<dd>
 				Define mechanisms for transitioning the computed values of CSS properties over time.