add end_angle to angle_axis

[LukaOber]

Adds end_angle to angle_axis. The feature was added in 5.5.0 and allows for polar slices. Will close #36

Example

Chart::new()
    .polar(PolarCoordinate::new())
    .tooltip(Tooltip::new())
    .angle_axis(
        AngleAxis::new()
            .type_(AxisType::Category)
            .end_angle(-180)
            .data(vec!["S1", "S2", "S3"]),
    )
    .radius_axis(RadiusAxis::new())
    .series(
        Bar::new()
            .coordinate_system(CoordinateSystem::Polar)
            .data(vec![1, 2, 3]),
    );

Will create this example plot polar-end-angle