UI: Center add-attachment link

client/components/cards/attachments.jade

@@ -49,4 +49,5 @@ template(name="attachmentsGalery")
                 | {{_ 'delete'}}
 
     if currentUser.isBoardMember
-      a.attachment-item.add-attachment.js-add-attachment {{_ 'add-attachment' }}
+      li.attachment-item.add-attachment
+        a.js-add-attachment {{_ 'add-attachment' }}

client/components/cards/attachments.styl

@@ -20,6 +20,10 @@
       display: flex
       align-items: center
 
+      a
+        display: block
+        margin: auto
+
     .attachment-thumbnail
       height: 80px
       display: flex