feat: Add support for custom icons in Question

[Flexonze]

Closes #1102

This is my first contribution to Copier. I appreciate the project and would welcome any feedback on the implementation :)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.25%. Comparing base (de88305) to head (bec18fb).
⚠️ Report is 7 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2381      +/-   ##
==========================================
+ Coverage   97.24%   97.25%   +0.01%     
==========================================
  Files          55       55              
  Lines        6247     6276      +29     
==========================================
+ Hits         6075     6104      +29     
  Misses        172      172              

Flag	Coverage Δ
unittests	97.25% <100.00%> (+0.01%)	⬆️

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[sisp]

Thanks for contributing this feature, @Flexonze! 🙇

It seems that some TUI assertions aren't accurate. Let me know if you need some help with debugging this. Other than that, everything looks great! 🥇

[Flexonze]

c32765e should fix the assertion issue. Hopefully it fixes the encoding problem too.

[sisp]

LGTM! Just one question – see inline comment.

[sisp]

Excellent work, @Flexonze! 🥇 Thanks for your contribution! 🙇