Document which properties are used by each feature

[jbothma]

Users sometimes aren't sure which properties are actually used by the matcher. I think part of the the issue is that some features apply to all properties of a given type, while some only apply to properties with a given name. That's not clear from the description. That could be added to the description, but it might be more readable if kept as a separate field.

It could be presented like this:

[jbothma]

@pudo Do we want this? Is this a sane way to go about it?

It's tempting to do this as structured data, but perhaps it's easier to see how realistic that is once we've done all the features as strings, and maybe that's over-engineering the slight over-engineering happening here already. So I'd propose a string only v1