Function closestPointToSegment

closestPointToSegment(c: Point, a: Point, b: Point): Point
Identify the point closest to C on segment AB
Parameters
- c: Point
  The reference point C
- a: Point
  Point A on segment AB
- b: Point
  Point B on segment AB
Returns Point
The closest point to C on segment AB

See
https://en.wikipedia.org/wiki/Distance_from_a_point_to_a_line#Line_defined_by_two_points