sameSideAs(vecA, vecB, vecC) {
    let d = this.whichSide(vecA, vecB);
    let dRef = vecC.whichSide(vecA, vecB);
    return d < 0 && dRef < 0 || d == 0 && dRef == 0 || d > 0 && dRef > 0;
  }
Checks whether or not this vector is on the same side of a line spanned by two vectors as another vector.

@param {Vector2} vecA A vector spanning the line.
@param {Vector2} vecB A vector spanning the line.
@param {Vector2} vecC A vector to check whether or not it is on the same side as this vector.
@returns {Boolean} Returns a boolean indicating whether or not this vector is on the same side as another vector.