Support csharp language versions 11, 12 and 13 (#402)

Author: BennyFranco

Sharpmake.Generators/VisualStudio/Csproj.cs

@@ -3430,7 +3430,10 @@ private Options.ExplicitOptions GenerateOptions(CSharpProject project, Project.C
             Options.Option(Options.CSharp.LanguageVersion.CSharp7_3, () => { options["LanguageVersion"] = "7.3"; }),
             Options.Option(Options.CSharp.LanguageVersion.CSharp8, () => { options["LanguageVersion"] = "8.0"; }),
             Options.Option(Options.CSharp.LanguageVersion.CSharp9, () => { options["LanguageVersion"] = "9.0"; }),
-            Options.Option(Options.CSharp.LanguageVersion.CSharp10, () => { options["LanguageVersion"] = "10.0"; })
+            Options.Option(Options.CSharp.LanguageVersion.CSharp10, () => { options["LanguageVersion"] = "10.0"; }),
+            Options.Option(Options.CSharp.LanguageVersion.CSharp11, () => { options["LanguageVersion"] = "11.0"; }),
+            Options.Option(Options.CSharp.LanguageVersion.CSharp12, () => { options["LanguageVersion"] = "12.0"; }),
+            Options.Option(Options.CSharp.LanguageVersion.CSharp13, () => { options["LanguageVersion"] = "13.0"; })
             );
 
             SelectOption(

Sharpmake/Options.CSharp.cs

@@ -478,6 +478,9 @@ public enum LanguageVersion
                 CSharp8,
                 CSharp9,
                 CSharp10,
+                CSharp11,
+                CSharp12,
+                CSharp13,
             }
 
             // Disable warning MSB3270 when disabled