add nchar as arguement to writeZarrArray

[Artur-man]

Missing nchar gives error with text array

> mat <- array(rep("text",231145), dim = c(231145))
> path_to_new_zarr <- file.path("data/string_test.zarr")
> writeZarrArray(x = mat, zarr_array_path = path_to_new_zarr, chunk_dim = c(10000))
Error in .check_datatype(data_type = data_type, fill_value = fill_value,  : 
  The 'nchar' argument must be provided and be a positive integer

however now:

> writeZarrArray(x = mat, zarr_array_path = path_to_new_zarr, chunk_dim = c(10000), nchar = 4)
<231145> ZarrArray object of type "character":
[1]      [2]      [3]      .        [231144] [231145] 
  "text"   "text"   "text"        .       ""       "" 

I am not sure about the empty text at the tail though but it seems the issue occurs with numeric values too

> mat <- array(rep(1,231145), dim = c(231145))
> path_to_new_zarr <- file.path("data/string_test.zarr")
> writeZarrArray(x = mat, zarr_array_path = path_to_new_zarr, chunk_dim = c(10000), nchar = 4)
<231145> ZarrArray object of type "double":
     [1]      [2]      [3]        . [231144] [231145] 
       1        1        1        .        0        0