Implement Gray code for bitline

[kitsuyui]

• Gray code is a binary numeral system where two successive values differ in only one bit
• https://en.wikipedia.org/wiki/Gray_code

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (0ea1693) to head (d42a2b6).

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #39   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         3           
  Lines          716       787   +71     
=========================================
+ Hits           716       787   +71     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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