Barcode text cutouts (#4)

* Proper textual cutouts in barcodes

This properly cuts out sections of the barcode to display text, between the endcaps and middle and shows prefix/checksum outside of the endcaps. It's slightly more complicated than it needs to be but this looks rather nice right now

* Fixed unit tests where possible

I had to remove `BarcodeTextView` tests because I couldn't figure out how to pass a GeometryReader.Proxy to the view.

* Cleaned up documentation

Made small font more legible, especially on 1x displays

Changed to fixed size text

Merge pull request #3 from nrivard/ConvertHStackToPath

Converted digit view to a Shape

Initial commit of `BarcodeView`.