QA: Separate footways that are not tagged as crossing

Similar to https://github.com/a-b-street/speedwalk/issues/76

I found ways like https://www.openstreetmap.org/way/1293979477/history that are clearly crossing in the sense that they cross a non-service(…) road but they dont have any crossing tagging.
Sometimes they are cut in the right way like here, where only the tagging is missing.
Sometimes the footway is drawn in one long line "over" the residential road in which case we need to split (https://github.com/a-b-street/speedwalk/issues/4) the crossing part of first.

查看关于拆分 footway 的 issue #4，以及关于 crossing 标记的 issue #76。检查 OSM way 示例，以了解几何和标记模式。代码可能会处理 OSM ways 来识别 crossings；定位用于 footway 拆分和 crossing 检测的相关模块。确定如何修改逻辑，以处理未标记的 crossings，并适当地拆分较长的 footways。

由索引模型根据 Issue 内容生成。