TurfMisc#nearestPointOnLine does not report distance along the route

Capturing from https://turfjs.org/docs/#nearestPointOnLine, the Feature returned from TurfMisc#nearestPointOnLine should return a location number property that describes the distance along the route of the computed intersection point, next to already available dist number property which describes the distance to the original point. Also would be great to explain those properties in the Javadoc and add public constant instead of relying on raw strings for dist and location.

/cc @cafesilencio

从 TurfMisc#nearestPointOnLine 开始，将其返回的 Feature 与 turfjs.org/docs/ 上的 nearestPointOnLine 文档进行比较。当结果包含路线距离 location 属性，并且 dist/location 属性在 Javadoc 中得到说明、由 public 常量替代原始字符串时，工作即完成。