Function to clean undershoots and overshoots

[luukvdmeer]

Is your feature request related to a problem? Please describe.
We have a lot of network cleaning functions implemented as spatial morphers now. One thing I am missing is a solution to Case I of the following:

Hence, edges are badly mapped which makes that they end just before they meet the other edge, resulting in a poorly connected network. This is also called an undershoot. Case II in the image is similar and could be supported additionally by changing a function argument for example. Case III is more related to map matching, see #114 . Next to undershoots, there are also overshoots. These are edges that have their endpoint shortly after crossing another edge, while in reality they should end on the other edge itself.

In sf there is the function st_snap which could help here, but it needs quite some tuning. Open for ideas!