[css-inline] Add ideographic and middle baselines as requested by SVG.

Author: fantasai

css-inline/Overview.bs

@@ -51,7 +51,7 @@ Dominant Baselines: the 'dominant-baseline' property</h3>
 
 	<pre class="propdef">
 	Name: dominant-baseline
-	Value: auto | text-bottom | alphabetic | central | mathematical | hanging | text-top
+	Value: auto | text-bottom | alphabetic | ideographic | middle | central | mathematical | hanging | text-top
 	Initial: normal
 	Applies to: block containers and inline boxes
 	Inherited: yes
@@ -81,6 +81,14 @@ Dominant Baselines: the 'dominant-baseline' property</h3>
 		<dd>
 			Use the alphabetic baseline.
 
+		<dt><dfn>ideographic</dfn>
+		<dd>
+			Match the box's ideographic character face under-side baseline to that of its parent.
+
+		<dt><dfn>middle</dfn>
+		<dd>
+			Use the “middle” baseline: halfway between the alphabetic baseline and the ex-height.
+
 		<dt><dfn>central</dfn>
 		<dd>
 			Use the central baseline
@@ -129,7 +137,7 @@ Alignment Point: 'alignment-baseline' longhand</h4>
 
 	<pre class="propdef">
 	Name: alignment-baseline
-	Value: baseline | text-bottom | alphabetic | middle | central | mathematical | text-top | bottom | center | top
+	Value: baseline | text-bottom | alphabetic | ideographic | middle | central | mathematical | text-top | bottom | center | top
 	Initial: baseline
 	Applies to: inline-level boxes
 	Inherited: no
@@ -158,6 +166,10 @@ Alignment Point: 'alignment-baseline' longhand</h4>
 		<dd>
 			Match the box's alphabetic baseline to that of its parent.
 
+		<dt><dfn>ideographic</dfn>
+		<dd>
+			Match the box's ideographic character face under-side baseline to that of its parent.
+
 		<dt><dfn>middle</dfn>
 		<dd>
 			Align the vertical midpoint of the box with