Add list reverse

For whatwg/html#12345.

Author: jakearchibald

infra.bs

@@ -1675,6 +1675,10 @@ a new <a>ordered set</a> |clone|, so that <a for=set>replacing</a> "<code>a</cod
 "<code>foo</code>" in |clone| gives « "<code>foo</code>", "<code>b</code>", "<code>c</code>" »,
 while |original|[0] is still the <a>string</a> "<code>a</code>".
 
+<p>To <dfn export for=list,stack,queue,set>reverse</dfn> a <a>list</a> |list| is to create a new
+<a>list</a> |reversed|, of the same designation, and, <a for=list>for each</a> |item| of |list|,
+<a for=list>prepend</a> |item| to |reversed|.
+
 <p>To <dfn export for=list,stack,queue,set lt="sort in ascending order|sorting in ascending order|sort|sorting">sort in ascending order</dfn>
 a <a>list</a> |list|, with a less than algorithm |lessThanAlgo|, is to create a new <a>list</a>
 |sorted|, containing the same <a for=list>items</a> as |list| but sorted so that according to