Add libraries for the UMUX and UMUX-Lite questionnaires

[shiyihe-neko]

Does this PR close any open issues?

It’s a feature I found useful for conducting user studies.

Give a longer description of what this PR addresses and why it's needed

This PR adds the UMUX (Usability Metric for User Experience) and UMUX-Lite questionnaires to the study library.

• UMUX is a short, standardized usability questionnaire developed as a concise and conceptually similar alternative to the System Usability Scale (SUS). It includes four items designed to assess how effective, efficient, and satisfying you find the system to use.
• UMUX-Lite is a two-item short-form usability measure (Lewis et al., 2013), designed for time-constrained user studies.

This implementation includes:

• JSON configuration for question structure and response format
• Markdown documentation (umux.md,umux-lite.md) describing the questionnaire and citation.

Are there any additional TODOs before this PR is ready to go?

TODOs:

• Update relevant documentation

[JackWilb]

Thanks for the PR @shiyihe-neko. I'm looking forward to this addition.

@tingying-he Please after we merge this can you generate the studies using the library (so users can find it more easily)

[JackWilb]

Should this be 7?

[tingying-he]

This should be 7

[JackWilb]

Should this be 7?

[tingying-he]

This should be 7

[tingying-he]

Yes, I can generate the studies after the library is merged. Please let me know when the merge is done. @JackWilb