Scroll overflowing tag tile contents

This is just a stopgap fix for flarum/core#653; I would like to revise the tag page layout at some point.

extensions/tags/less/forum/TagTiles.less

@@ -81,6 +81,7 @@
   bottom: 42px;
   padding-right: 20px;
   transition: background 0.2s;
+  overflow: auto;
 
   &:hover {
     background: fade(#000, 5%);