Document batch prediction arg

Closes #137 (closed)

docs/usage/predict.md

@@ -23,6 +23,7 @@ Use the `teklia-dan predict` command to apply a trained DAN model on an image.
 | `--line-separators`         | List of line separators.                                                                        | `list`  | `["\n"]`      |
 | `--threshold-method`        | Method to use for attention mask thresholding. Should be in `["otsu", "simple"]`.               | `str`   | `"otsu"`      |
 | `--threshold-value `        | Threshold to use for the "simple" thresholding method.                                          | `int`   | `0`           |
+| `--batch-size `             | Size of the batches for prediction.                                                             | `int`   | `1`           |
 
 ## Examples