Update default.html

Signed-off-by: David Rotermund <54365609+davrot@users.noreply.github.com>

_layouts/default.html

@@ -149,6 +149,10 @@
         th:empty {
           display: none; /* This will make an empty header cell vanish */
         }    
+
+        table, th, td {
+          border: 2px solid white; /* 2px lines for cells and header */
+        }
         
         img {
           display: block;