add yt colormaps as cmyt_names

[andrew-saydjari]

Adding a few more colormaps for astronomers, from the yt project.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 50.37%. Comparing base (d250262) to head (869bbf3).
⚠️ Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
src/ColorSchemes.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #149      +/-   ##
==========================================
- Coverage   50.75%   50.37%   -0.39%     
==========================================
  Files           1        1              
  Lines         132      133       +1     
==========================================
  Hits           67       67              
- Misses         65       66       +1     

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[andrew-saydjari]

I think this is ready for review (and that the codecov test should be ignored, but let me know if that is not true).