[css-anchor-position-1] Add missing keywords to <<position-area>> <dl> #11372

Author: fantasai

css-anchor-position-1/Overview.bs

@@ -27,6 +27,7 @@ spec:css-position-3;
 	type:property; text:inset-inline-start
 spec:css-cascade-5; type:dfn; text:property
 spec:dom; type:dfn; text:shadow tree
+spec:css-align-3; type:value; for:<self-position>; text:center
 </pre>
 
 <pre class=anchors>
@@ -697,12 +698,12 @@ by specifying the rows and columns the region occupies as follows:
 		are identical,
 		but refer to the box's own [=writing mode=].
 
-	: <dfn>span-start</dfn>, <dfn>span-end</dfn>
+	: <dfn>span-start</dfn>, <dfn>span-end</dfn>, <dfn>span-self-start</dfn>, <dfn>span-self-end</dfn>
 	: <dfn>span-top</dfn>, <dfn>span-bottom</dfn>
-	: <dfn>span-y-start</dfn>, <dfn>span-y-end</dfn>
-	: <dfn>span-x-start</dfn>, <dfn>span-x-end</dfn>
-	: <dfn>span-block-start</dfn>, <dfn>span-block-end</dfn>
-	: <dfn>span-inline-start</dfn>, <dfn>span-inline-end</dfn>
+	: <dfn>span-y-start</dfn>, <dfn>span-y-end</dfn>, <dfn>span-y-self-start</dfn>, <dfn>span-y-self-end</dfn>
+	: <dfn>span-x-start</dfn>, <dfn>span-x-end</dfn>, <dfn>span-x-self-start</dfn>, <dfn>span-x-self-end</dfn>
+	: <dfn>span-block-start</dfn>, <dfn>span-block-end</dfn>, <dfn>span-self-block-start</dfn>, <dfn>span-self-block-end</dfn>
+	: <dfn>span-inline-start</dfn>, <dfn>span-inline-end</dfn>, <dfn>span-self-inline-start</dfn>, <dfn>span-self-inline-end</dfn>
 	:: Two adjacent rows or columns,
 		depending on which axis this keyword is specifying:
 		the center row/column,