add documentation for new 1D plotting functionalities

[JoshuaLampert]

This adds some more documentation for the two new features regarding 1D plots implemented in #2250 and #2258 as requested in #2250 (comment).

[github-actions]

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[sloede]

Thanks a lot!

[JoshuaLampert]

Auto-merge doesn't work because the required CI runs don't run. So someone with superpower needs to merge this manually.

[ranocha]

The doc build fails since SciML/DiffEqBase.jl#1115 needs to be merged and released. We will wait for it and merge this PR when the Documenter.jl CI job passes.

[ChrisRackauckas]

Sorry it should come quickly. Long story short, some constructors in SplitFunction referred to that arg as _func_cache while the type name was cache. It's an undocumented argument so we can change it around, but it wasn't an issue until we started using things like Accessors.jl which assume the availability of keyword arguments with the right name. So there were some errors being thrown around in remake for a few months that I isolated to this, but the fix isn't so clean because it involves changing an undocumented name across two repos. But my hope is all tests in SciMLBase/DiffEqBase/OrdinaryDiffEq should be green after this 🤞

[sloede]

[...] It's an undocumented argument so we can change it around, but it wasn't an issue until we started using things like Accessors.jl [...]

Obligatory xkcd reference:

Thanks a lot for fixing this 🙏

[JoshuaLampert]

DiffEqBase.jl v6.163.0 is out and fixes the problem. Thanks @ChrisRackauckas!