Multi-ion Compressible Euler's Equations

[warisa-r]

This PR contains the implementation of the code relating to the multi-ion Euler's equations in 1- and 2D, including the example parallel with the example for the MHD equations. I open a new PR to separate the code for the Euler-Poisson from this implementation. Please let me know if there is anything wrong!

[github-actions]

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[DanielDoehring]

Sweet, thanks! We should loosely keep an eye on what is happening with the Multi-Ion MHD equations and adjust accordingly here.