Add Color to allowable types for fill_color and line_color.

[jrmobley]

Adds support for color opacity values to ExportSVG fill_color and line_color.

[codecov]

Codecov Report

Attention: Patch coverage is 96.87500% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 96.34%. Comparing base (ec495d5) to head (a788605).

Files	Patch %	Lines
src/build123d/exporters.py	96.87%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #573      +/-   ##
==========================================
+ Coverage   96.30%   96.34%   +0.03%     
==========================================
  Files          24       24              
  Lines        7776     7787      +11     
==========================================
+ Hits         7489     7502      +13     
+ Misses        287      285       -2     

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[gumyr]

Thanks!