Update Cell.php

Author: terryzwt

src/PhpWord/Style/Cell.php

@@ -34,6 +34,10 @@ class Cell extends Border
      * Top to Bottom, Right to Left.
      */
     const TEXT_DIR_TBRL = 'tbRl';
+    /**
+     * Top to Bottom, Right to Left, Vertical
+     */
+    const TEXT_DIR_TBRLV = 'tbRlV';
     /**
      * Bottom to Top, Left to Right.
      */