Feature request: option to make start/end of polyline non-editable

[leiflinse-trivector]

I tried to take all but first and last marker, but it appears that they are ordered not along the line, but grouped by point type, so one would have to take that into account when deciding which points to remove, at which point this feels like I am getting too deep into implementation specific details of this library.

polyEditor.edit().sublist(1, polyEditor.edit().length - 2)

So I think it would be better if there is an option to disable the first and last marker. Perhaps two independent flags, as there may also be use cases where you only want to fixate one of the ends.