Add strokestyle attribute to Box

[nHackel]

Hello! I've recently used the Box with cornerradius to create a plot and wanted to adapt the stroke style and found no option to do that.

Description

This PR adds the strokestyle keyword to a Box:

For the implementation I also had to adapt a check for compatible linestyles in CairoMakie, which was incompatible with the return type of convert_attribute for key"linestyle.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• Added an entry in NEWS.md (for new features and breaking changes)
• Added or changed relevant sections in the documentation
• Added reference image tests for new plotting functions, recipes, visual options, etc.

[jkrumbiegel]

Hi, thanks for the PR! I think we call that property linestyle everywhere, even if other properties have stroke as a prefix. But might as well keep in line with that linestyle convention for now

[nHackel]

Ah, okay! I'm essentially building my first more involved Makie figure and haven't used many keywords so far.

In src/makielayout/types.jl I saw a few types with x- prefix but they also seem to have multiple linestyles per type. I can adapt it to linestyle.

Do you think image reference tests are necessary and if so could you point me in the right direction? I was mainly following your rounded corner PR and haven't strayed too far from files you changed there, so a bit unsure of the testing is setup

[jkrumbiegel]

Just renaming strokestyle to linestyle will be enough here.

Reference images are good practice, it's hard to unit-test visual attributes otherwise. You could add a test for Box here https://github.com/MakieOrg/Makie.jl/blob/master/ReferenceTests/src/tests/figures_and_makielayout.jl, just a Figure with a couple boxes, each of which exercises some of the functionality. And it's good to make the differences salient, like using thick strokes, big rounded corners, etc, so that visual changes are picked up well.

[jkrumbiegel]

Thanks, looks good!