Improve accessibility, specifically for color-blind folks

[jeroenheijmans]

There are accessible descriptions of all visuals. But there's also a bunch of people who can't distinguish colors well enough, while still seeing the graphs. We can easily improve things for them:

• Consider using pointStyle for line graphs (and their legends)
• Consider using fill patterns for bar charts (and their legends)
• Consider making one of both of those optional as they might hurt accessibility for other folks because of the clutter it adds?

[jeroenheijmans]

Point style for line graphs was added in 2022. The fill patterns will have to come later (it also has to be pretty of course!), if someone wants to propose a PR I'm open to that.