:sparkles: Pyro theme

[BattleCh1cken]

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Summary

Adds a new theme based on Pyro's Spin Up notebook.

Checklist

• [ ] I have fully tested all of the added features
• [ ] I have fully documented all of the relevant code
• [ ] finish the appendix entries
• [ ] finish the frontmatter entries
• [ ] finish all of the rudimentary components
  • [x] toc
  • [ ] decision matrix
  • [ ] pro/con
  • [ ] glossary
• [ ] finalize the cover