[css-logical-1] Define interpretation of caption-side: left|right (as line-relative).

Author: fantasai

css-logical-1/Overview.bs

@@ -181,10 +181,14 @@ Logical Values for the 'caption-side' Property</h3>
 
   These two values are added only for implementations that support
   ''caption-side/left'' and ''caption-side/right'' values for 'caption-side'.
+  The ''caption-side/left'' and ''caption-side/right'' values themselves
+  are defined to be <a>line-relative</a>.
+
   The existing ''caption/top'' and ''caption/bottom'' values are idiosyncratically redefined
   as assigning to the <a>block-start</a> and <a>block-end</a> sides of the table, respectively.
-  The mapping on this property uses the <a>writing mode</a> of the element’s <a>containing block</a>
-  (that is, the table wrapper box).
+
+  The mapping on this property uses the <a>writing mode</a> of the caption’s <a>containing block</a>
+  (that is, the <a>table wrapper box</a>).
 
 <h3 id="float-clear">
 Flow-Relative Values for the 'float' and 'clear' Properties</h3>