Use mandatory keyword arguments instead of positional arguments?

In most example files, we have

viscosity = ArtificialViscosityMonaghan(0.02, 0.0)

If you're not familiar with the API, you'd have to check the Julia help to see that the first positional argument is alpha and the second is beta.
In many places, we do this instead:

alpha = 0.02
viscosity = ArtificialViscosityMonaghan(alpha, 0.0)

This makes it clear that the first positional argument is alpha, and it allows us to overwrite this with trixi_include. However, doing this everywhere will create quite a bit of extra code.

We could also use mandatory keyword arguments, so that the line above becomes

viscosity = ArtificialViscosityMonaghan(alpha=0.02, beta=0.0)

Here, we can natively use trixi_include without further modification.

The Trixi.jl API is slowly moving away from positional arguments for exactly this reason. But they often allow both options:
https://github.com/trixi-framework/Trixi.jl/blob/276dc3ca22a4c72b81aa6659e57ff1382dd1ae0c/src/solvers/dgsem/dgsem.jl#L54-L69

Do we want to

1. keep things like they are?
2. have keyword arguments instead of positional arguments?
3. allow both?

I don't like option 3, as it makes the API more complicating by adding more options to do the same thing.

Review the example files using ArtificialViscosityMonaghan and compare their positional argument usage with Trixi.jl's src/solvers/dgsem/dgsem.jl lines 54-69. Check how trixi_include handles alpha and beta overrides, then establish the preferred constructor style and make the affected examples consistent with that decision.