Added support for mergeCells, cell height, shrink to fit

Added support for
    mergeCells:
        // mergeCells (B2:G2), you may use CellHelper::getColumnLettersFromColumnIndex() to convert from "B2" to "[1,2]"
	    $writer->mergeCells([1,2], [6, 2]);

    cell height:
        $row->setHeight(30);

    shouldShrinkToFit:
        $style->setShouldShrinkToFit();

These changes are implemented for XLSX as that's what I need and test spout on.

src/Spout/Writer/XLSX/Manager/OptionsManager.php

@@ -39,6 +39,8 @@ class OptionsManager extends OptionsManagerAbstract
             Options::DEFAULT_ROW_STYLE,
             Options::SHOULD_CREATE_NEW_SHEETS_AUTOMATICALLY,
             Options::SHOULD_USE_INLINE_STRINGS,
+            Options::COLUMN_WIDTHS,
+            Options::MERGE_CELLS,
         ];
     }
 
@@ -56,5 +58,7 @@ class OptionsManager extends OptionsManagerAbstract
         $this->setOption(Options::DEFAULT_ROW_STYLE, $defaultRowStyle);
         $this->setOption(Options::SHOULD_CREATE_NEW_SHEETS_AUTOMATICALLY, true);
         $this->setOption(Options::SHOULD_USE_INLINE_STRINGS, true);
+        $this->setOption(Options::COLUMN_WIDTHS, []);
+        $this->setOption(Options::MERGE_CELLS, []);
     }
 }