Add algorithm for Newton's Law of Gravitation (#6626)

* Add algorithm for Newton's Law of Gravitation

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Update physics/newtons_law_of_gravitation.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* One and only one argument must be 0

* Update newtons_law_of_gravitation.py

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>