Should standardization functions accept non-string values as valid input?

[yutanagano]

For a lot of use cases, you want to blanket apply tidytcells' standardization function to columns of a table, with some cells missing values. Currently, the standardize functions expect the first argument to be a string, so being passed Nones or nans triggers an exception. For now, users are expected to handle that themselves, but should there be an option to handle that quietly within tidytcells?