Added missing overload for speed. (SpecificEnergy=Speed*Speed)

Author: Erik Ovegard

UnitsNet.Tests/CustomCode/SpeedTests.cs

@@ -119,5 +119,13 @@ public void TimeSpanTimesSpeedEqualsLength()
             Length length = TimeSpan.FromSeconds(2)*Speed.FromMetersPerSecond(20);
             Assert.AreEqual(length, Length.FromMeters(40));
         }
+
+        [Test]
+        public void SpeedTimesSpeedEqualsSpecificEnergy()
+        {
+            //m^2/s^2 = kg*m*m/(s^2*kg) = J/kg
+            SpecificEnergy length = Speed.FromMetersPerSecond(2) * Speed.FromMetersPerSecond(20);
+            Assert.AreEqual(length, SpecificEnergy.FromJoulesPerKilogram(40));
+        }
     }
 }

UnitsNet/CustomCode/UnitClasses/Speed.extra.cs

@@ -54,5 +54,10 @@ public partial struct Speed
         {
             return Length.FromMeters(speed.MetersPerSecond*duration.Seconds);
         }
+
+        public static SpecificEnergy operator *(Speed left, Speed right)
+        {
+            return SpecificEnergy.FromJoulesPerKilogram(left.MetersPerSecond * right.MetersPerSecond);
+        }
     }
 }