[Redesign] Set a max-width on Graphviz

Summary: Ref T8750, Adds a maxwidth class for Graphviz images.

Test Plan: Generate a Graphviz image, really big, see it scale to the viewport.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T8750

Differential Revision: https://secure.phabricator.com/D13548

src/infrastructure/markup/interpreter/PhabricatorRemarkupGraphvizBlockInterpreter.php

@@ -42,12 +42,13 @@ final class PhabricatorRemarkupGraphvizBlockInterpreter
       return '<'.$file->getBestURI().'>';
     }
 
-    return phutil_tag(
+    $img = phutil_tag(
       'img',
       array(
         'src' => $file->getBestURI(),
         'width' => nonempty($width, null),
       ));
+    return phutil_tag_div('phabricator-remarkup-embed-image-full', $img);
   }
 
   // TODO: This is duplicated from PhabricatorEmbedFileRemarkupRule since they