feat: ✨ add "writing Python" guide section (#48)

# Description

Section in guide for writing Python code.

Closes #15
Closes #16
Closes #6
Closes #4


This PR needs an in-depth review.

## Checklist

- [x] Formatted Markdown
- [x] Ran `just run-all`

---------

Co-authored-by: martonvago <57952344+martonvago@users.noreply.github.com>
Co-authored-by: Signe Kirk Brødbæk <40836345+signekb@users.noreply.github.com>

Author: 3 people

_quarto.yml

@@ -31,6 +31,7 @@ book:
         - iterations/end.qmd
     - part: "Python"
       chapters:
+        - python/code.qmd
         - python/tests.qmd
     - part: "Operations"
       chapters: