first draft IMEX JinXin

[MarcoArtiano]

I made a first dirty and "straightforward" draft, but as I anticipated it might have some bugs. I still didn't generalize to keep it simple until I'm sure it will work. I broke it down to the simplest way to make it work, but I couldn't find any major mistakes.

[github-actions[bot]]

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Created with :heart: by the Trixi.jl community.

[MarcoArtiano]

There was a missing sign on my implementation, now the code seems to run well. I'm gonna make further test, clean up everything and improve the implementation where is possible.

[ranocha]

Could you please run the code formatter as described in https://trixi-framework.github.io/Trixi.jl/stable/styleguide/?

[MarcoArtiano]

Could you please run the code formatter as described in https://trixi-framework.github.io/Trixi.jl/stable/styleguide/?

Done!

[JoshuaLampert]

Looks like you used another version of the JuliaFormatter for formatting resulting in many unrelated changes, see also #1976. Can you rerun the formatter with the other version, please?