Add the grams force unit

Common/UnitDefinitions/Force.json

@@ -31,6 +31,24 @@
         }
       ]
     },
+    {
+      "SingularName": "GramForce",
+      "PluralName": "GramsForce",
+      "FromUnitToBaseFunc": "{x} * 9.80665e-3",
+      "FromBaseToUnitFunc": "{x} / 9.80665e-3",
+      "XmlDocSummary": "The gram-force is a unit of force equal to the magnitude of force exerted by a gram of mass in standard gravity (9.80665 m/s²). It is equal to 9.80665 × 10⁻³ N.",
+      "XmlDocRemarks": "https://en.wikipedia.org/wiki/Kilogram-force",
+      "Localization": [
+        {
+          "Culture": "en-US",
+          "Abbreviations": [ "gf" ]
+        },
+        {
+          "Culture": "ru-RU",
+          "Abbreviations": [ "гс" ]
+        }
+      ]
+    },
     {
       "SingularName": "KilogramForce",
       "PluralName": "KilogramsForce",

Common/UnitEnumValues.g.json

@@ -469,7 +469,8 @@
     "Poundal": 12,
     "PoundForce": 13,
     "ShortTonForce": 14,
-    "TonneForce": 15
+    "TonneForce": 15,
+    "GramForce": 16
   },
   "ForceChangeRate": {
     "CentinewtonPerSecond": 1,

UnitsNet.Tests/CustomCode/ForceTests.cs

@@ -10,6 +10,7 @@ public class ForceTests : ForceTestsBase
         protected override double DecanewtonsInOneNewton => 1E-1;
         protected override double DyneInOneNewton => 1E5;
 
+        protected override double GramsForceInOneNewton => 0.1019716e3;
         protected override double KilogramsForceInOneNewton => 0.1019716;
 
         protected override double KilopoundsForceInOneNewton => 0.2248089e-3;
@@ -110,5 +111,12 @@ public void KilogramForceDividedByNewtonEqualsStandardGravity()
             var duration = Force.FromKilogramsForce(1) / Force.FromNewtons(1);
             Assert.Equal(9.80665, duration);
         }
+
+        [Fact]
+        public void ThousandGramsForceEqualsOneKilogramForce()
+        {
+            var force = Force.FromGramsForce(1000);
+            Assert.Equal(Force.FromKilogramsForce(1), force.ToUnit(ForceUnit.KilogramForce));
+        }
     }
 }