add polar plot with error bands

Hi! I have a feature request. It would be nice if the plotly.express polar plot functions would also have error_y / error_y_minus options in order to draw error bands. This would allow users to inspect group differences in a multivariate space quickly. The issue is further described on stackoverflow. The idea would be that each group gets its own trace. For each variable in theta, Samples within each group can be used to estimate the mean and some sort of confidence interval (e.g. SEM).

Start with the plotly.express polar plot functions and review the linked Stack Overflow example. Determine how grouped samples should produce per-variable means and confidence intervals, including the roles of error_y and error_y_minus. Done means each group can render its own polar trace with error bands and the behavior is covered by appropriate tests.