Add doc with common Data Valuation benchmarks / tasks

[mdbenito]

Just short descriptions and links to the functions implementing / helping with them

• Data removal / addition
• Outlier detection
• Data debugging
• etc.

[mdbenito]

I have written a long-ish blog post about this and added just a few keywords to the documentation in #404. Instead of copying it we should just link to it once we release a stable version and publish the post.

[AnesBenmerzoug]

If I'm not mistaken, this was taken care of in #492