Document along behaviour when distance is outside line length range

lib/src/along.dart

@@ -3,7 +3,10 @@ import 'package:turf/destination.dart';
 import 'package:turf/helpers.dart';
 import 'package:turf/src/distance.dart' as measure_distance;
 
-/// Takes a [line] and returns a [Point] at a specified distance along the line.
+/// Takes a [line] and returns a [Point] at a specified [distance] along the line.
+///
+/// If [distance] is less than 0, the line start point is returned
+/// If [distance] is larger than line length, the end point is returned
 Point? along(LineString line, num distance, [Unit unit = Unit.kilometers]) {
   // Get Coords
   final coords = line.coordinates;