[css-anchor-position-1] Add the x-self-start/etc variants too, to be consistent.

Author: tabatkins

css-anchor-position-1/Overview.bs

@@ -369,12 +369,14 @@ Animation type: TBD
 
 <pre class=prod>
 <dfn>&lt;inset-area-span></dfn> =
+	[ start || end || center ] |
+	[ self-start || self-end || center ] |
 	[ top || bottom || center ] |
 	[ left || right || center ] |
 	[ x-start || x-end || center ] |
 	[ y-start || y-end || center ] |
-	[ start || end || center ] |
-	[ self-start || self-end || center ] |
+	[ x-self-start || x-self-end || center ] |
+	[ y-self-start || y-self-end || center ] |
 	all
 </pre>
 
@@ -448,26 +450,24 @@ and/or the "end region" between the last two.
 	:: All three regions of that axis,
 		spanning the entire breadth of the containing block.
 
-	: <dfn>start</dfn>
-	: <dfn>end</dfn>
-	: <dfn>self-start</dfn>
-	: <dfn>self-end</dfn>
+	: <dfn>start</dfn>, <dfn>end</dfn>, <dfn>self-start</dfn>, <dfn>self-end</dfn>
+	: <dfn>top</dfn>, <dfn>bottom</dfn>, <dfn>left</dfn>, <dfn>right</dfn>
+	: <dfn>y-start</dfn>, <dfn>y-end</dfn>, <dfn>y-self-start</dfn>, <dfn>y-self-end</dfn>
+	: <dfn>x-start</dfn>, <dfn>x-end</dfn>, <dfn>x-self-start</dfn>, <dfn>x-self-end</dfn>
 	: <dfn>center</dfn>
-	: <dfn>top</dfn>
-	: <dfn>bottom</dfn>
-	: <dfn>y-start</dfn>
-	: <dfn>y-end</dfn>
-	: <dfn>left</dfn>
-	: <dfn>right</dfn>
-	: <dfn>x-start</dfn>
-	: <dfn>x-end</dfn>
 	:: Any single keyword refers just to that region in the axis.
 
 		Like in ''anchor()'',
-		''inset-area/start'' and ''inset-area/end''
-		refer to the writing mode of the element's [=containing block=],
-		while ''inset-area/self-start'' and ''inset-area/self-end''
-		refer to the element's own writing mode.
+		the plain logical keywords
+		(''inset-area/start'', ''inset-area/end'', etc)
+		refer to the writing mdoe of the element's [=containing block=].
+		The ''inset-area/x-start''/etc determine their direction in the same way,
+		but in the specified physical axis.
+
+		The "self" logical keyword
+		(''inset-area/self-start'', ''inset-area/x-self-end'', etc)
+		are identical,
+		but refer to the element's own writing mode.
 
 	: two keywords
 	:: Refers to the area spanned by the two indicated regions.