Provide document of numeric types and type stability

[huiyuxie]

Covers #1909. It is just a start and later I will add more documentation.

[github-actions]

Review checklist

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Created with ❤️ by the Trixi.jl community.

[ranocha]

Thanks.

[huiyuxie]

Please check again now :)

First, please check style, I try to keep consistency with the rest of the convention file. Second, concerning content, I think handling these cases on a case-by-case basis is acceptable for now (but I have no idea if this is good for other developers). Third, I suggest asking someone unfamiliar with these things to review it again. While you understand it clearly, it may not be as easy for others to grasp.

[huiyuxie]

Shall we merge this PR if it looks good to you, or should it be held until the main PR is ready to merge?

I think I should check the main PR again based on your provided notes. Please wait

[ranocha]

Thanks! This looks good to me. It would be nice to get feedback from @sloede next. Then, we can merge this PR and continue with the other ones.

[sloede]

Thanks a lot for adding this to the docs! I only have some small suggestions for adding additional context, plus some formatting changes (I'd use proper subheadings such that we can directly link to them)

[sloede]

Thanks for bearing with me @huiyuxie! I've made a new suggestion, where I leave your original part about exact FP values virtually unchanged, but add some clarification later.

Once these final remarks are resolved, this is ready to merge 😊

[sloede]

Thanks!

[huiyuxie]

Thanks, these are good suggestions!

[ranocha]

Thanks!