need to determine an object signature for file related output

[patrickkettner]

since there will likely be a number of testers that lint/audit code on a line-by-line basis, it makes sense to ensure that all of those plugins follow a certain type of format so that reports can iterate over all of them easily.

since we can't really programmatically detect this sort of thing (I think?), we can't enforce it via joi or anything (at least for now) so this should ultimately just be a docs update