Add Support for UPC-A Barcodes

[primo-ppcg]

Hi, I would like to use the Viewer in my app for viewing the labels. It draws everything except UPC Barcode. Would it possible that you add UPC codes to the viewer aswell? This is the ZPL for my UPC Barcode (in Labelary it works):

^XA
^BY4,2,66^FO70,179^BUN,,Y,N,Y^FD1234567890000^FS
^XZ

Originally posted by @yatsek1 in #253

[kyleweishaupt]

Hi, I am running into this issue as well using the ^BUN command. My application can print and it shows up in the Labelary overlay, but not through the viewer. Hoping this feature can be implemented in the near future.