Created jest tests for password_gen.js

[LaserBread]

Pull Request Template

Description

Created Jest test cases for the password_gen.js file, mostly so I could test my Jest skills.

Checklist:

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• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have added tests that prove my fix is effective or that my feature works.
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[MigrainePanda]

generateOTP() doesn't type check for int but isn't a problem for this PR. Looks good