[css-writing-modes] Add back aliases for block-size/inline-size. Add in old anchors so links will still work.

Author: fantasai

css-writing-modes/Overview.bs

@@ -1485,10 +1485,12 @@ Abstract Dimensions</h3>
         axis</i> in horizontal writing modes and the <i>vertical axis</i>
         in vertical writing modes.</dd>
     <dt><dfn lt="block size | block-size">block size</dfn>
+    <dt id=extent><dfn>logical height</dfn>
       <dd>A measurement in the block dimension:
         refers to the physical height (vertical dimension) in horizontal writing modes,
         and to the physical width (horizontal dimension) in vertical writing modes.
     <dt><dfn lt="inline size | inline-size">inline size</dfn>
+    <dt id=measure><dfn>logical width</dfn>
       <dd>A measurement in the inline dimension:
         refers to the physical width (horizontal dimension) in horizontal writing modes,
         and to the physical height (vertical dimension) in vertical writing modes.