Network: Connect Footway<>Centerline to Generated Sidewalk

Example:
* https://a-b-street.github.io/speedwalk/#17.66/52.763668/13.246949
* https://www.mapillary.com/app/?pKey=1623087731621290&focus=photo&lat=52.7641425&lng=13.2451492&z=17

I just added the crossing=informal to signal that the only way to use this footway is to just cross the road and cross the grass-verge.

I did not add the separate crossing way given that it is only an informal crossing, so the separate sidewalk is not connected.

Do we expect the "generate corssings" step to add the missing link here?
I kind of did but I am not sure…

---

Related https://github.com/a-b-street/speedwalk/issues/70

The issue is about connecting a footway to a generated sidewalk when an informal crossing exists. Look at the 'generate crossings' step in the codebase, likely in a network generation module. Examine how crossings are currently linked and where footway and sidewalk geometries are handled. Check the provided Mapillary and speedwalk links to understand the real-world scenario. Determine if the algorithm should automatically create a link for informal crossings or if manual intervention is needed.

Written by the indexing model from the issue text.