Barcode value is being cut off

## Problem
It looks like this library doesn't calculate the viewbox properly when rendering a jagged UPC barcode with the value printed underneath.

## Example

```js
JsBarcode('#barcode', '673006885997', {
format: 'UPC',
width: 2,
height: 32
});
```

## Expected

## Actual

(Notice the barcode value being cut off at the bottom.)

Start by reproducing the JavaScript example in the issue with format UPC, width 2, and height 32, then inspect the barcode rendering path that calculates the viewBox. Done means the value printed beneath the jagged barcode is fully visible rather than clipped, matching the expected rendering.

Written by the indexing model from the issue text.