Add Type Hints to simulate_data.py

[louismagowan]

Closes #378

---

📚 Documentation preview 📚: https://causalpy--544.org.readthedocs.build/en/544/

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.52%. Comparing base (828ba2e) to head (d6449bb).

Files with missing lines	Patch %	Lines
causalpy/data/simulate_data.py	75.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #544      +/-   ##
==========================================
- Coverage   95.59%   95.52%   -0.07%     
==========================================
  Files          29       29              
  Lines        2681     2684       +3     
==========================================
+ Hits         2563     2564       +1     
- Misses        118      120       +2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[louismagowan]

@drbenvincent codecov failure seems irrelevant for a PR that just adds type hints right? These were pre-existing issues right, or am I missing something?