Add boxes in bias_leaderboard

[Sbozzolo]

In this next iteration of the leaderboard, I am now using Makie boxplot.

Draw a Tukey style boxplot. The boxplot has 3 components:

• a crossbar spanning the interquartile (IQR) range with a midline marking the median
• an errorbar whose whiskers span range * iqr
• points marking outliers, that is, data outside the whiskers

I tried plotting individual models to see how they would look like, but I couldn't get something that is properly readable. I can highlight specific models, if some are more useful/important than others.

[Sbozzolo]

[szy21]

Thanks!