Area vs Arc

[Erlicht]

Given the potentially difficult interpretation of areas, an option to show just the arc for the confidence intervall would be nice. So just draw the dots in the last x rows before the border instead of from the origin to the border.

[FSchwendinger]

• Addressed by including the area_arc argument, allowing the user to specify the size of the fan. 0 produces a complete fan. E.g. 0.95 creates an arc.