FEAT Add VLSU dataset

[romanlutz]

Is your feature request related to a problem? Please describe.

New multimodal dataset dropped that's not integrated yet!

https://github.com/apple/ml-vlsu/

The work to enable this is likely similar to what was done for harmbench-multimodal.

Comment below if interested and feel free to ask questions first.

[riyosha]

I'd like to take this up