In case of cell value "__proto__" exceljs creates invalid file.
Same happens also with CellHyperlinkValue.text = "__proto__"

Steps to repro:
1. Create new excel file and worksheet.
2. Add rows to the sheet:
        sheet.addRow(["Not good"]);
        sheet.addRow(["__proto__"]);
3. Save the file.

Expected result:
Excel file with two text cells with provided values.

Actual result:
LibreOffice shows the file, but second row data is invalid.
Excel claims that the file is invalid. If force-opened, shows [object Object] in second cell