`pair_ann` does not work with `data.table`

> pair_ann(x = df_example, on = "txt")
  First data set:  8 records
  Second data set: 8 records
  Total number of pairs: 10 pairs
  Blocking on: 'txt'

       .x    .y block
    <int> <int> <num>
 1:     1     2     1
 2:     1     3     1
 3:     1     4     1
 4:     2     3     1
 5:     2     4     1
 6:     5     6     2
 7:     5     7     2
 8:     5     8     2
 9:     6     7     2
10:     6     8     2
> pair_ann(x = setDT(df_example), on = "txt")
Error: j (the 2nd argument inside [...]) is a single symbol but column name 'on' is not found. If you intended to select columns using a variable in calling scope, please try DT[, ..on]. The .. prefix conveys one-level-up similar to a file system path.

ncn-foreigners / blocking

`pair_ann` does not work with `data.table` #16