change codes to use png instead of jpg

[johnfercher]

Description

• this will improve quality of qr-code, matrix-code and barcode.
• related to feature/barcodes-in-png #465

Related Issue

Checklist

check with "x", ONLY IF APPLIED to your change

• All methods associated with structs has func (<first letter of struct> *struct) method() {} name style.
• Wrote unit tests for new/changed features.
• Followed the unit test when,should naming pattern.
• All mocks created with m := mocks.NewConstructor(t).
• All mocks using m.EXPECT().MethodName() method to mock methods.
• Updated docs/doc.go and docs/*
• Updated example_test.go.
• Updated README.md
• New public methods/structs/interfaces has comments upside them explaining they responsibilities
• Executed make dod with none issues pointed out by golangci-lint

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.09%. Comparing base (268b9c0) to head (dd006fc).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #483      +/-   ##
==========================================
+ Coverage   87.03%   87.09%   +0.07%     
==========================================
  Files          61       61              
  Lines        2319     2330      +11     
==========================================
+ Hits         2018     2029      +11     
  Misses        268      268              
  Partials       33       33              

Flag	Coverage Δ
unittests	87.09% <100.00%> (+0.07%)	⬆️

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