Extent calculation doesn't account for radius of Points #693

Just fixed scverse/spatialdata-plot#334 and noticed that the extent calculation does not account for the radius of points. In the first version of this picture we calculated this within spatialdata-plot but that has since moved upstream. It's realistically not super noticeable if these are small, but f.e. in our test case it stands out:

Can be mitigated through the pad_extent parameter in sdata.pl.show(), but figured I'd report anyway.