* Standardized handling of SHC data to generate receipt objects
* Added examples of decoded SHC data for ease of reference and for knowledge-sharing
* Refactored decoder to make logic more standardized for cross-region decoding, and
eliminated most special-case handling
* Added rejection of non-verified SHC issuers for card generation
* Added rejection of non-COVID SHC cards for card generation
Ryan Slobojan