Add todo item for grouping broken links by link target

doc/todo/brokenlinks_should_group_links_to_a_page.mdwn

@@ -0,0 +1,9 @@
+I would find the [[plugins/brokenlinks]] listing much easier to use if it
+grouped all the links to a single missing page on one line, rather than showing
+one line per page that links to the missing page.
+
+I think this would work well as the default; however, if people prefer the
+current behavior, perhaps brokenlinks could have an option to group by link
+target.
+
+--[[JoshTriplett]]