Provide path for each Hocon node

[lostiniceland]

It would be great if a Hocon node could also yield its current path in the document.

It should merely be a additional field in the Hocon-enum, though I could be missing some complexity since I currently have no idea how this nom parser macros work and I assume you need the information from there.

[mockersf]

it should be possible with nom, but I'm using an old version (4.2) when current (6.1) changed a lot and is nicer to use

when trying to update, I encountered an issue (rust-bakery/nom#1021) that makes it harder to follow the Hocon spec... I should try again, that was quite some time ago