Migrate colorcet to using pixi for development

[Azaya89]

This PR migrates the developer workflow to Pixi. This is aligned with what has already been done for holoviews and hvPlot:

• Create pixi.toml to use approach adopted by hvPlot
• Ensure the tests / docs / build workflow work as expected
• Create the developer guide page in the docs

[hoxbro]

It's a great first iteration of this migration. I have left some comments for you (and one for me).

I haven't read the developer_guide.md, but if you haven't already, double-check that everything is also valid for colorcet.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.89%. Comparing base (34b3992) to head (5f3f9c6).
Report is 5 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #128       +/-   ##
===========================================
+ Coverage   85.70%   95.89%   +10.19%     
===========================================
  Files           8        6        -2     
  Lines        1938     1609      -329     
===========================================
- Hits         1661     1543      -118     
+ Misses        277       66      -211     

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[hoxbro]

I don't think you have pushed the changes to this PR.

[Azaya89]

I don't think you have pushed the changes to this PR.

Done now.

[hoxbro]

Looks like we are almost there.

Can you thoroughly look at the changes and ensure that nothing is missed?

Also, remember to open an issue about dropping EOL Python versions.

[Azaya89]

I think everything is fine now...

[hoxbro]

PyPi publish step failed: https://github.com/holoviz/colorcet/actions/runs/13862842237/job/38795500998

[hoxbro]

Fixed in #129

[hoxbro]

Other than that, everything went great with a dev release.

Great job!

[Azaya89]

Thank you for the help!