Add a ConvertFormula function

In Excel VBA we have this function:

Application.ConvertFormula

This function allows us to convert a formula in several ways, including changing from A1 reference style to R1C1 reference style and changing the cell references from relative to absolute and vice versa.

Another nice thing about it is that it generates an error if the formula is invalid, so we can use this function to check if a formula string is valid, without writing the formula to a cell.

IMO it would be beneficial to have such a function implemented in the office-js API for Excel.