Fix invalid UPC-E in some cases

[shinbin]

Hi, DavBfr:
I found an issue in UPC-E barcode and fixed it.

One of the cases had a UPC-E input value of "100802" or "01008029".
The barcode content I expect to be displayed is "01008029" , as shown in the 1st picture,
but it displays '01020089' and cannot be read by the barcode scanner , as shown in the 2nd picture.
There are also errors in other input values, such as 107444,100902,100965,555555,1.. etc.

The issue comes from upcaToUpce() , whose RegExp cannot split groups accurately.
Please help to check and merge my fixed version.

Thanks.

OK, Test site : https://www.online-barcode.com/barcode-generator or https://barcodeqrcode.com/upc-e-generator/

NG, Test site : https://davbfr.github.io/dart_barcode/#/

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (7197206) 84.08% compared to head (7d1edd1) 84.04%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master      #66      +/-   ##
==========================================
- Coverage   84.08%   84.04%   -0.05%     
==========================================
  Files          32       32              
  Lines        2300     2294       -6     
==========================================
- Hits         1934     1928       -6     
  Misses        366      366              

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[shinbin]

@DavBfr
If you have time, please check out the pull request.
Thanks.