[css-align] Add issue for unsafe default alignment.

Author: fantasai

css-align/Overview.bs

@@ -401,6 +401,14 @@ Overflow Alignment: the ''safe'' and ''unsafe'' keywords</h3>
 	If the <a>overflow alignment</a> isn't explicitly specified,
 	the default <a>overflow alignment</a> is ''unsafe''.
 
+	Issue: This creates problems for people with small windows
+	since overflow to the start direction is unreachable.
+	We are considering having an omitted overflow alignment indicate a “smart” safe behavior,
+	which would true-align the alignment subject
+	unless it would overflow the nearest <em>scroll container</em>,
+	at which point it would cease to shift startward
+	so that it continued to remain within the scrollable area.
+
 	<pre class='prod'><dfn>&lt;overflow-position></dfn> = unsafe | safe</pre>
 
 	<dl dfn-type="value" dfn-for="<overflow-position>">