Query functions are missing return values/no consistent docu style

[maunzCache]

Hi everyone I am ready the documentation for the query functions at https://prometheus.io/docs/prometheus/latest/querying/functions/ for the very first time when i noticed this issue.

A handful of functions to state their return value in the description text but not all do. You can only get to know the return value of a function if you try it or if its documented in the text. It would be nice if there was a uniform syntax for that documentation so one can see the return value instantly.

E.g. given idelta(v range-vector) you may write it as idelta(v range-vector): instance-vector
I don't know how a proper syntax would look like but i hope the idea of this issue is clear. If not feel free to ask questions.

[brian-brazil]

We're currently putting it in the prose for them, so should probably follow that elsewhere.