rowSpan does not seem to work
when using the following data on the sample page (https://catamphetamine.gitlab.io/write-excel-file/)
```json
[
[
{
"value": "Name",
"fontWeight": "bold",
"rowSpan": 2
},
{
"value": "Date"
},
{
"value": "Cost",
"fontWeight": "bold"
},
{
"value": "Paid",
"fontWeight": "bold"
}
],
[
{
"value": ""
},
{
"value": new Date(),
"type": Date,
"format": "mm/dd/yyyy"
},
{
"value": 1800,
"type": Number,
"format": "#,##0.00"
},
{
"value": true,
"type": Boolean
}
],
[
{
"value": "Alice Brown",
"type": String
},
{
"value": new Date(),
"type": Date,
"format": "mm/dd/yyyy"
},
{
"value": 2599.99,
"type": Number,
"format": "#,##0.00"
},
{
"value": false,
"type": Boolean
}
]
]
```
the columns A1 and A2 should be merged, however, this does not seem to work.
Normal span appears to work fine.
issue