Add array formula support to Excel Office JS API

See https://stackoverflow.com/questions/47402660/how-to-enter-array-formulas explaining the issue.

Setting an array formula like this is not working:

let sheet = context.workbook.worksheets.getActiveWorksheet(); 1
let range = sheet.getRange("A31")
range.formulas = [["{=INDEX(Data!$A$2:$A$35;MATCH(0;COUNTIF(A$1:$A9;Data!$A$2:$A$35);0))}"]]
await context.sync();