Document `@testsetup`

[MilesCranmer]

I noticed from the tests there is this @testsetup which is very useful for my work:

https://github.com/julia-vscode/TestItemRunner.jl/blob/main/test/runtests.jl

Would be good to have documentation on this as I am curious about the entire API and any caveats to be aware of.

[davidanthoff]

That doesn't work yet, though :) I've just started the implementation, but it is not yet done.

[MilesCranmer]

Oh I see, thanks for clarifying