Add Vector2D.ToPoint2D() method with unit test (#235)

* Add Vector2D.ToPoint2D() method with unit test

* Improve comments

---------

Co-authored-by: Michele Castellazzi <michele.castellazzi@technoprobe.com>

Author: mymike00

src/Spatial.Tests/Euclidean/Point2DTests.cs

@@ -146,6 +146,13 @@ public void DistanceTo(string p1s, string p2s, double expected)
             Assert.AreEqual(expected, p2.DistanceTo(p1));
         }
 
+        [TestCase("-1 ; 2")]
+        public void ToVectorAndBack(string ps)
+        {
+            var p = Point2D.Parse(ps);
+            AssertGeometry.AreEqual(p, p.ToVector2D().ToPoint2D(), 1e-9);
+        }
+
         [TestCase("0, 0", "1, 2", "0.5, 1")]
         [TestCase("-1, -2", "1, 2", "0, 0")]
         public void MidPoint(string p1s, string p2s, string eps)

src/Spatial/Euclidean/Vector2D.cs

@@ -475,6 +475,15 @@ public Vector2D Add(Vector2D v)
             return new Vector2D(X + v.X, Y + v.Y);
         }
 
+        /// <summary>
+        /// Returns a point, whose position vector is equal to the current vector
+        /// </summary>
+        /// <returns>A point</returns>
+        public Point2D ToPoint2D()
+        {
+            return new Point2D(this.X, this.Y);
+        }
+
         /// <summary>
         /// Transforms a vector by multiplying it against a provided matrix
         /// </summary>

src/Spatial/Euclidean/Vector3D.cs

@@ -523,7 +523,7 @@ public Vector3D Rotate(UnitVector3D about, Angle angle)
         }
 
         /// <summary>
-        /// Returns a point equivalent to the vector
+        /// Returns a point, whose position vector is equal to the current vector
         /// </summary>
         /// <returns>A point</returns>
         public Point3D ToPoint3D()