[css-color-5] Update changes section to 20 April 2021

Author: svgeesus

css-color-5/Overview.bs

@@ -992,13 +992,29 @@ Changes {#changes}
 <h3 id="changes-20200303">Since the <a href="https://www.w3.org/TR/2020/WD-css-color-5-20200303/">FPWD of 10 June 2020</a></h3>
 
 <ul>
-	<!--
-	<li>Added `in` keyword before <<color-space>> tokens in functions</li>
-	<li>Removed adjusters from color-mix</li>
-	-->
-	<!-- to 28 Jan 2021 -->
-	<!-- removed interpolation section changes, added to Color 4 -->
-	<!-- to 5 Jan 2021 -->
+
+	<!-- to 20 Apr 2021 -->
+	<li>Consistently used the term color space rather than colorspace,
+		defined <<color-space>> token
+	</li>
+	<li>Corrected color-contrast grammar</li>
+	<li>Added an optional target contrast ratio to color-contrast()</li>
+	<li>Corrected adjuster grammar</li>
+	<li>Noted that the corner case of percentages summing to zero needs to be handled</li>
+	<li>Clarified order of operations in color-mix()</li>
+	<li>Updated examples to match current grammar</li>
+	<li>Defined how percentages are normalized</li>
+	<li>Clarify meaning of 0% and 100% in color-mix()</li>
+	<li>Definition of adjusters moved from color-mix() to color-adjust()</li>
+	<li>Allow arguments to color-mix() to be in any order</li>
+	<li>Mandatory color space for color-mix()</li>
+	<li>Allowed the percentage in color-mix() to come before the color</li>
+	<li>Added explicit algorithm for color-mix()</li>
+	<li>Removed adjusters from color-mix() and simplified the grammar</li>
+	<li>Added the "in" keyword to specify the color space used for mixing</li>
+	<li>Required color-contrast() list to have at least two items</li>
+	<li>Improved explanation of the relative color syntax</li>
+	<!-- removed interpolation section changes, added to changes of Color 4 -->
 	<li>Link to CSS 4 definition of color serialization</li>
 	<li>Added separate section for color spaces</li>
 	<li>Updated color-adjust example</li>