Add derivative(t) method to BezierCurve class

[nsree0507]

Describe your change:

• [ ] Add an algorithm? Added a derivative(t) method to the BezierCurve class to compute the tangent vector at any point t on the curve. This supports curves of any degree and is useful for animation, motion planning, and curve analysis.

Checklist:

• [x] I have read CONTRIBUTING.md.
• [x] This pull request is all my own work -- I have not plagiarized.
• [x] I know that pull requests will not be merged if they fail the automated tests.
• [x] This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• [x] All new Python files are placed inside an existing directory.
• [x] All filenames are in all lowercase characters with no spaces or dashes.
• [x] All functions and variable names follow Python naming conventions.
• [x] All function parameters and return values are annotated with Python type hints.
• [x] All functions have doctests that pass the automated testing.
• [x] All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• [x] This pull request resolves issue number: Fixes #13861