Add ODE case study

[SamuelBrand1]

Draft PR for work on adding the case study recreating part of the Chatzilena paper.

NBs:

• Reduced nadapts and ndraws temporarily, for faster rendering.
• Added julia YAML section to index.qmd because it doesn't seem to be being added from the _quarto.yml config file (unknown reason).

Tasks

• Add first pass in same structure to other case studies that renders.
• Go back through to reduce amount of writing
• Go back through with emphasis on more reusability (mainly plotting functions)
• Consider updating figure from 2x2 to 2x3 as per other examples.
• Put nadapts and ndraws back to standard values (1000 each).

[seabbs]

Closing in favour of #90