ENH: Handle walking areas as part of the network

[HTenkanen]

I also have a question related to this. In the OSM data there are walking areas (such as inside train stations and large sidewalks and public "squares" (of various shapes). I attached an example with many of these pedestrian areas.

These are polygon ways in OSM, and they are areas where people can walk. However, when generating the walking network, and especially when exporting it to NetworkX,, my expectation is that these polygons are simply removed.

If they are not simply removed, please describe how they are handled in the documentation. But if they are removed...

...in terms of accessibility, it seems it would be better to interpret them as part of the network. My plan was to simply make the polygon boundary a LinearRing or LineString. The next issue would be, are they even connected to the surrounding network? In many cases I think not, which would bring us back to our other discussion about automatically connecting disconnected components.

Originally posted by @bramson in https://github.com/HTenkanen/pyrosm/issues/67#issuecomment-729540054