feat: added derivative and second derivative approximations

[Ajadamson206]

Description of Change

Added two new files to the numerical methods directory.

File 1: differentiation_midpoint.c -> Uses the symmetric derivative to calculate the derivative for any function at x as long as x is defined

File 2: differentiation_second_mid.c -> Uses the second derivative three-point midpoint formula to calculate the second derivative for any function at x as long as x is defined

References

Checklist

• [x ] Added description of change
• [ x] Added file name matches File name guidelines
• [ x] Added tests and example, test must pass
• [ x] Relevant documentation/comments is changed or added
• [ x] PR title follows semantic commit guidelines
• [ x] Search previous suggestions before making a new one, as yours may be a duplicate.
• [ x] I acknowledge that all my contributions will be made under the project's license.

Notes:

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