Pie chart initial slice angle

Hi,

I'm not aware of any way to configure the initial slice angle for a `pygal.Pie`. For example, I have three equal slices and I want the first slice to start at 300°, it should look like this:


Is this a feature that Pygal might support? If not, is there any workaround, perhaps using custom CSS?

Thanks!

Start by finding the pygal.Pie rendering and configuration entry points and checking existing tests for pie output. Confirm how an initial slice angle should be represented, then add coverage and verify that a pie with three equal slices can start at 300°.

Written by the indexing model from the issue text.