[css-ruby] Add rule to trim leading/trailing white space

Author: fantasai

css-ruby/Overview.html

@@ -568,6 +568,14 @@ <h3 id=box-fixup><span class=secno>2.2. </span> Anonymous Ruby Box
      href="http://lists.w3.org/Archives/Public/www-style/2013Sep/0160.html">wrapping
      content</a> within ruby annotations anyway.
 
+   <dt id=anony-gen-trim-space>Trim leading/trailing white space
+
+   <dd> Any white space within a ruby structure is discarded at the beginning
+    and end of a <a href="#ruby-container-box"><i>ruby container</i></a>, <a
+    href="#ruby-annotation-container-box"><i>ruby annotation
+    container</i></a>, or <a href="#ruby-base-container-box"><i>ruby base
+    container</i></a>.
+
    <dt id=anon-gen-bare-inlines>Wrap misparented inline-level content
 
    <dd> Any consecutive sequence of text and inline-level boxes directly

css-ruby/Overview.src.html

@@ -299,6 +299,12 @@ <h3 id="box-fixup">
 			since we might need to handle
 			<a href="http://lists.w3.org/Archives/Public/www-style/2013Sep/0160.html">wrapping content</a> within ruby annotations anyway.
 
+		<dt id="anony-gen-trim-space">Trim leading/trailing white space
+		<dd>
+			Any white space within a ruby structure is discarded
+			at the beginning and end of
+			a <i>ruby container</i>, <i>ruby annotation container</i>, or <i>ruby base container</i>.
+
 		<dt id="anon-gen-bare-inlines">Wrap misparented inline-level content
 		<dd>
 			Any consecutive sequence of text and inline-level boxes