Add viewport to the address

[gabipurcaru]

hey @aloisdeniel! When doing geocoding and showing the result on the map, it's very useful to know the bounding box of the place, especially when not looking up something very exact (e.g. a national park). Google provides this in the viewport property:

I'm adding this to the Google version of the geocoder - not sure how to do it for the local one (and I don't really need it for my personal project).

Let me know what you think of this PR.