Added support for cell formats when writing Excel files

src/Spout/Writer/Common/Manager/Style/StyleMerger.php

@@ -88,6 +88,9 @@ class StyleMerger
         if (!$style->getBorder() && $baseStyle->shouldApplyBorder()) {
             $styleToUpdate->setBorder($baseStyle->getBorder());
         }
+        if (!$style->getFormat() && $baseStyle->shouldApplyFormat()) {
+            $styleToUpdate->setFormat($baseStyle->getFormat());
+        }
         if (!$style->shouldApplyBackgroundColor() && $baseStyle->shouldApplyBackgroundColor()) {
             $styleToUpdate->setBackgroundColor($baseStyle->getBackgroundColor());
         }