Created Unassigned: row outlineLevel is ignored [14921]

I have a file created by EPPlus. The file has grouping rows (outline). When EPPlus reads the file, it ignores row.OutlineLevel. Here is the problem and the fix (*):

ExcelWorksheet.cs
```
if (xr.AttributeCount > 2 ||
(xr.AttributeCount == 2 && xr.GetAttribute("spans") != null) ||
(*) (xr.AttributeCount == 2 && xr.GetAttribute("outlineLevel") != null))
{
rowList.Add(AddRow(xr, row));
}
```
I added (*) line.

Inside XLSX I see:

```
<row r="3" outlineLevel ="1" ><c r="A3" s="0" t="s"><v>21</v></c></row>
```

Is the fix OK? Can I apply it, would it break something?