Please add the ability to include the hatching/stroke_style used for a particular data series in the legend

For colorblind users, having the legend include more than just the color is helpful to them. Currently, they can see the colors, but charts may not be as useful if they cannot distinguish between them well.

The only workaround is to turn off individual series to isolate the one they need, but that doesn't help if they need to compare two series.

Start by locating the legend rendering entry point and the code that stores or draws each series' hatching or stroke_style. Trace how legend items are generated, then determine how the legend can expose those styles alongside colors. Done means series with distinct hatching or stroke styles are distinguishable in the legend while existing chart legends remain correct.

Written by the indexing model from the issue text.