Support hex code inputs for colors

[BradyAJohnston]

Supports supplying a string hex code for the InputString when using the python API. The nodes can't directly take it, but the supplied string will be parsed to linear sRGB and the values set on the color property.

g.Color("#ff8000")

[codecov]

Codecov Report

❌ Patch coverage is 86.95652% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.44%. Comparing base (6cd8457) to head (f66c61c).

Files with missing lines	Patch %	Lines
src/nodebpy/builder/node.py	80.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #84      +/-   ##
==========================================
- Coverage   97.46%   97.44%   -0.02%     
==========================================
  Files          65       65              
  Lines       17962    17985      +23     
==========================================
+ Hits        17506    17526      +20     
- Misses        456      459       +3     

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