Automatically shift bottom legend down if the x-axis labels rotate / get longer

[my-tien]

When positioning the legend at the bottom of the chart, the placement works nicely if tick labels take up only one line. But if the labels take up more vertical space, they will draw over the legend.

It would be nice if the legend could be pushed down automatically to account for the extra space required.

Corresponding codepen

As discussed before, let's revisit this in 6 - 8 weeks time when hopefully there will be more capacity for this complex issue.

[my-tien]

FYI
@stephprobst @emilykl @gvwilson