Run doctests in testing suite

[cgarling]

This should run the doctests as part of the test suite. I don't expect this to pass now because of printing / environment stuff that we probably need to be more careful about when writing the doctests.

[giordano]

I don't understand why you need eval: https://github.com/EnzymeAD/Enzyme.jl/blob/c009fa593821cbd9017450a6721259f7dbc6ebf1/test/doctests.jl

[cgarling]

Thanks for the tip. I added the @eval approach to fix failures with Documenter.jl not recognizing the package module (see here). This problem only appeared when I switched to ParallelTestRunner so I may just be configuring something improperly. The errors are things like

│ ┌ Error: Failed to evaluate `CurrentModule = AstrochemicalYields` in `@meta` block.
│ │   exception =
│ │    UndefVarError: `AstrochemicalYields` not defined in `Main`
│ │    Suggestion: check for spelling errors or missing imports.
│ │    Hint: AstrochemicalYields is loaded but not imported in the active module Main.

I fixed this by explicitly importing the package into Main using @eval.

Looking at the code in Enzyme it's not clear to me why this error occurs in my project but not in Enzyme because Enzyme has a similar @meta block in their index.md file. Any tips would be appreciated

[giordano]

JuliaTesting/ParallelTestRunner.jl#68. It's not always necessary, but if the output depends on the exact module where the code is being evaluated, then something like that may be needed.