Optional ReadonlycategoryRead the category cells' displayed text and the header cell before them.
Needs ExcelApi 1.15: pass Office.context.requirements.isSetSupported( 'ExcelApi', '1.15'). Default false.
Optional ReadonlyimageRead the chart's image as Excel draws it: true at the chart's own size,
or a width to scale it to. Default false.
Options for readExcelChart.