Add first fundamental form calculator to maths

[singhc7]

This adds a script to calculate the coefficients (e, f, g) of the first fundamental form for parametric surfaces. This mathematical framework is a core concept in differential geometry, used to measure lengths, angles, and areas on a surface.

The implementation uses sympy for symbolic differentiation and simplification. While standard mathematical notation dictates capital E, F, and G for these coefficients, they are implemented as lowercase to strictly adhere to PEP 8 N806 and pass the repository's required Ruff linter pre-commit hooks.

Reference: https://en.wikipedia.org/wiki/First_fundamental_form

Author: singhc7

Describe your change:

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• Documentation change?

Checklist:

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