fix: change order is contributing doc

[jamiechicago312]

• I have read and reviewed the documentation changes to the best of my ability.
• If the change is significant, I have run the documentation site locally and confirmed it renders as expected.

Summary of changes
Based on feedback from @jpelletier1 testing a PR locally, I have swapped the contributing doc order so setting up dev environment is higher.

Only 1 doc changed
Only order of contents changed.

[all-hands-bot]

🟢 Good taste - Pragmatic reordering based on real user feedback. The new flow is more logical: introduce → set up environment → contribution workflow → explore what you can build. No complexity added, no content changed, just a simple fix that solves an actual usability problem.