add splitOn

[ggPeti]

I'm rude. My code is good. Accept the PR for the code or reject it for the person's rudeness. The choice is yours.

[Janiczek]

For reviewers: the intuitive sense as to why this doesn't need any List.reverse nor ++ is that instead of tail-optimization it explodes the calculation into many nested function calls.

@ggPeti I think it could be useful to mention in the doc comment for the function that this keeps the delimiters

[miniBill]

Doesn't this cause a stack overflow for very long lists?

[ggPeti]

@Janiczek thanks, isn't "starting with each element" clear in communicating that? that was my intention

@miniBill yes it does. It's a purposefully stack-utilizing recursive function.

[miniBill]

I think one of the requisites we have for -extra functions is that they are stack safe.

By the way, the PR should probably be against elmcraft/core-extra.

[ggPeti]

I refuse to submit PRs to elmcraft/core-extra. And requiring stack safety indiscriminately is just silly and no such guarantee is documented in this library.

[miniBill]

Acknowledged

[ggPeti]

Hi @Chadtech could you please approve the checks?