Add TemperatureDelta / Duration = TemperatureChangeRate (#1370)

Added missing operator to divide a TemperatureDelta by a time/duration
to get the TemperatureChangeRate.

---------

Co-authored-by: Andreas Gullberg Larsen <andreas.larsen84@gmail.com>

UnitsNet.Tests/CustomCode/TemperatureDeltaTests.cs

@@ -64,5 +64,19 @@ public void TemperatureDeltaTimesEntropyEqualsEnergy()
             Energy energy = TemperatureDelta.FromKelvins(20) * Entropy.FromJoulesPerKelvin(4);
             Assert.Equal(Energy.FromJoules(80), energy);
         }
+
+        [Fact]
+        public void TemperatureDeltaDividedByTimeSpanEqualsTemperatureChangeRate()
+        {
+            TemperatureChangeRate changeRate = TemperatureDelta.FromKelvins(20) / TimeSpan.FromSeconds(2);
+            Assert.Equal(TemperatureChangeRate.FromDegreesCelsiusPerSecond(10), changeRate);
+        }
+
+        [Fact]
+        public void TemperatureDeltaDividedByDurationEqualsTemperatureChangeRate()
+        {
+            TemperatureChangeRate changeRate = TemperatureDelta.FromKelvins(20) / Duration.FromSeconds(2);
+            Assert.Equal(TemperatureChangeRate.FromDegreesCelsiusPerSecond(10), changeRate);
+        }
     }
 }

UnitsNet/CustomCode/Quantities/TemperatureDelta.extra.cs

@@ -1,6 +1,8 @@
 // Licensed under MIT No Attribution, see LICENSE file at the root.
 // Copyright 2013 Andreas Gullberg Larsen (andreas.larsen84@gmail.com). Maintained at https://github.com/angularsen/UnitsNet.
 
+using System;
+
 namespace UnitsNet
 {
     public partial struct TemperatureDelta
@@ -40,5 +42,17 @@ public partial struct TemperatureDelta
         {
             return temperatureDelta.Kelvins * cte.PerKelvin;
         }
+
+        /// <summary> Get <see cref="TemperatureChangeRate"/> from <see cref="TemperatureDelta"/> divided by <see cref="TimeSpan"/>.</summary>
+        public static TemperatureChangeRate operator /(TemperatureDelta temperatureDelta, TimeSpan timespan)
+        {
+            return TemperatureChangeRate.FromDegreesCelsiusPerSecond(temperatureDelta.Kelvins / timespan.TotalSeconds);
+        }
+
+        /// <summary> Get <see cref="TemperatureChangeRate"/> from <see cref="TemperatureDelta"/> divided by <see cref="Duration"/>.</summary>
+        public static TemperatureChangeRate operator /(TemperatureDelta temperatureDelta, Duration duration)
+        {
+            return TemperatureChangeRate.FromDegreesCelsiusPerSecond(temperatureDelta.Kelvins / duration.Seconds);
+        }
     }
 }