Add support for railway platforms as a multipolygon in some cases.

[supersquidgirl]

OSMI link for the issue: https://tools.geofabrik.de/osmi/?view=routing&lon=23.80372&lat=38.04217&zoom=19

As part of my efforts to achieve "inbox zero" on my account, I have been working to resolve as many OSMI errors for elements that were last edited by me. However, there are some errors that need to be addressed here as potential false positives.

This issue describes such a situation that I discovered, where the OSM Inspector currently does not detect a railway platform if it is a multipolygon, without exceptions.

According to this OSM Wiki page, a railway platform can be a multipolygon if at least one of the ways that make up said multipolygon is a platform edge, using the tag railway=platform_edge.

Some Athenian railway stations along the median of the A6 Attiki Odos motorway have adopted this scheme to indicate where the platform edges are, and which of the platform edges correspond to any given service (Metro or Suburban Railway).

Screenshot attached for reference: