Add S(q) simulation scripts

[andkerr]

Description

This PR is a follow up to the recently-merged Static Structure Factor example notebook. It adds scripts to freud-examples that allow the systems used in notebook examples to be replicated.

Checklist:

• I agree with the terms of the freud Contributor Agreement.
• My code follows the code style of this project.
• I have updated the index notebook if needed.
• My name is on the contributors list.

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[andkerr]

I have added a script which runs the LJ 1000-particle simulation that is used in the notebook. I wasn't sure what to name or where to store the file, so right now it is StaticStructureFactor-LJ.py, located at examples/StaticStructureFactor-LJ/StaticStructureFactor-LJ.py.

This PR can also include a citation / link to the code that generates the GeS2 simulation shown later in the notebook.