Center the plot legends under figure title

[jikaczmarski]

We would like to see the chart legends centered.

[jikaczmarski]

Used my browsers element inspector to find the .plot-d6a7b5-swatches-wrap selector was being applied to every legend in the web book. I wrote the following into styles.css,

.plot-d6a7b5-swatches-wrap {
    justify-content: center;
}

This made all legends centered across the web book.