Add Turbidity Unit (#842)

Author: rgomez90

Common/UnitDefinitions/Turbidity.json

@@ -0,0 +1,20 @@
+{
+  "Name": "Turbidity",
+  "BaseUnit": "NTU",
+  "XmlDoc": "Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality.",
+  "XmlDocRemarks": "https://en.wikipedia.org/wiki/Turbidity",
+  "Units": [
+    {
+      "SingularName": "NTU",
+      "PluralName": "NTU",
+      "FromUnitToBaseFunc": "x",
+      "FromBaseToUnitFunc": "x",
+      "Localization": [
+        {
+          "Culture": "en-US",
+          "Abbreviations": ["NTU"]
+        }
+      ]
+    }
+  ]
+}

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

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+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by \generate-code.bat.
+//
+//     Changes to this file will be lost when the code is regenerated.
+//     The build server regenerates the code before each build and a pre-build
+//     step will regenerate the code on each local build.
+//
+//     See https://github.com/angularsen/UnitsNet/wiki/Adding-a-New-Unit for how to add or edit units.
+//
+//     Add CustomCode\Quantities\MyQuantity.extra.cs files to add code to generated quantities.
+//     Add UnitDefinitions\MyQuantity.json and run generate-code.bat to generate new units or quantities.
+//
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+// Licensed under MIT No Attribution, see LICENSE file at the root.
+// Copyright 2013 Andreas Gullberg Larsen ([email protected]). Maintained at https://github.com/angularsen/UnitsNet.
+
+using System;
+
+namespace UnitsNet.Tests.CustomCode
+{
+    public class TurbidityTests : TurbidityTestsBase
+    {
+        // Override properties in base class here
+        protected override double NTUInOneNTU => 1;
+    }
+}