[Feature] : Add gravitational field calculator

[Ajita369]

Description

This calculator will calculate the gravitational field of the planet given its mass and radius by the user.

Screenshots

No response

Checklist

• [X] I have checked the existing issues.
• [X] I follow Contributing Guidelines of this project.
• [X] I am a GSSOC'24 contributor.
• [ ] I am a IWOC'24 contributor.
• [ ] I am a JWOC'24 contributor.
• [ ] I am a SWOC'24 contributor.

Code of Conduct

• [X] I agree to follow this project's "Code of Conduct".