Add TrajectoryData type checks to public API

[schroedtert]

Closes #524

[codecov]

Codecov Report

❌ Patch coverage is 44.73684% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.08%. Comparing base (9e87735) to head (2de8cb5).

Files with missing lines	Patch %	Lines
pedpy/methods/method_utils.py	46.15%	7 Missing ⚠️
pedpy/methods/acceleration_calculator.py	14.28%	6 Missing ⚠️
pedpy/methods/speed_calculator.py	55.55%	4 Missing ⚠️
pedpy/methods/spatial_analysis.py	33.33%	2 Missing ⚠️
pedpy/methods/density_calculator.py	66.66%	1 Missing ⚠️
pedpy/methods/flow_calculator.py	66.66%	1 Missing ⚠️

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