Add milliGauss to MagneticField (#917)

Author: cabusto

Common/UnitDefinitions/MagneticField.json

@@ -14,7 +14,7 @@
       "PluralName": "Teslas",
       "FromUnitToBaseFunc": "x",
       "FromBaseToUnitFunc": "x",
-	    "Prefixes": [ "Nano", "Micro", "Milli" ],
+      "Prefixes": [ "Nano", "Micro", "Milli" ],
       "Localization": [
         {
           "Culture": "en-US",
@@ -27,6 +27,7 @@
       "PluralName": "Gausses",
       "FromUnitToBaseFunc": "x/1e4",
       "FromBaseToUnitFunc": "x*1e4",
+      "Prefixes": [ "Milli" ],
       "Localization": [
         {
           "Culture": "en-US",

UnitsNet.NumberExtensions.Tests/GeneratedCode/NumberToMagneticFieldExtensionsTest.g.cs

@@ -33,5 +33,6 @@ public class MagneticFieldTests : MagneticFieldTestsBase
         protected override double MicroteslasInOneTesla => 1e6;
         protected override double MilliteslasInOneTesla => 1e3;
         protected override double GaussesInOneTesla => 1e4;
+        protected override double MilligaussesInOneTesla => 1e7;
     }
 }