remove numeric check on lag_vec() function

[mitokic]

Hey Matt and team,

I was hoping you could remove the numeric check in the lag_vec() function. I'd like to use lag_vec() within tk_augment_lags() to create lag variables for things like holidays, which are character/factor values. This will help in leveraging lags/leads in time series machine learning models with non-numeric regressors.

I've checked that the xts::lag.xts() function works as intended with non-numeric data. Please see the code below.

Numeric Value
timetk::m4_monthly %>% dplyr::group_by(id) %>% dplyr::mutate(lag_1 = lag_vec(value, lag = 3))

Factor/Character Value
timetk::m4_monthly %>% dplyr::group_by(id) %>% dplyr::mutate(id = as.character(id), lag_1 = xts::lag.xts(x = id, k = 3, na.pad = TRUE))

Please let me know what you think. Thank you!