Support unit testing in submitty_test script

[ziesski]

Currently submitty_test supports php-lint, js-lint, css-lint To get equal coverage on local machine as github CI, it would need to support unit testing as well. Yet, some subtlety involves using package npm script. For more detail you may look #9918

[github-actions[bot]]

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[williamschen23]

Solved by https://github.com/Submitty/Submitty/pull/11802