[css-ruby-1] Add note about about shaping across ruby element boundaries to address <https://lists.w3.org/Archives/Public/www-style/2014Aug/0049.html>.

Author: fantasai

css-ruby-1/Overview.bs

@@ -1272,6 +1272,12 @@ Sharing Annotation Space: the 'ruby-merge' property</h3>
 		</dd>
 	</dl>
 
+	Note: Text does not shape or form ligatures
+	across [=ruby annotations=] or [=ruby base|bases=],
+	even merged ones,
+	due to [=bidi isolation=].
+	See [[#bidi]] and [[#css-text-3#boundary-shaping]].
+
 <h3 id="ruby-align-property"><span id="rubyalign"></span>
 Ruby Text Distribution: the 'ruby-align' property</h3>