title: How to make header bold on excel when export in angular 12
body: <p>I am trying to make the header in bold in excel while exporting but i am not able find solution, my code is</p>
  <pre><code> public exportExcel(jsonData: any[], fileName: string): void {
      const ws: XLSX.WorkSheet = XLSX.utils.json_to_sheet(jsonData);
      const wb: XLSX.WorkBook = { Sheets: { 'data': ws }, SheetNames: ['data'] };
  
      const excelBuffer: any = XLSX.write(wb, { bookType: 'xlsx', type: 'array',cellStyles:true });
  
      this.saveExcelFile(excelBuffer, fileName);
    }
  
    private saveExcelFile(buffer: any, fileName: string): void {
      const data: Blob = new Blob([buffer], { type: this.fileType });
      FileSaver.saveAs(data, fileName + this.fileExtension);
    }
  </code></pre>
  <p>i want to find solution here to add style for header.</p>