Catch suspicious strings inside template tags

[jwarby]

It would be nice to be able to capture situations like the following, where the hardcoded string 'Unkown User' could be output by the template if user.name is not set (EJS example):

<div class="user-info">
   <h1><%= user.name || 'Unknown User' %></h1>
   <!-- ....snip... -->
</div>