Add TimeSpan string converter (#1718)

Author: GabeDeBacker

src/System.CommandLine.Tests/Binding/TypeConversionTests.cs

@@ -568,6 +568,28 @@ public void Values_can_be_correctly_converted_to_nullable_Guid_without_the_parse
             value.Should().Be(Guid.Parse(guidString));
         }
 
+        [Fact]
+        public void Values_can_be_correctly_converted_to_TimeSpan_without_the_parser_specifying_a_custom_converter()
+        {
+            var timeSpanString = "30";
+            var option = new Option<TimeSpan>("-x");
+
+            var value = option.Parse($"-x {timeSpanString}").GetValueForOption(option);
+
+            value.Should().Be(TimeSpan.Parse(timeSpanString));
+        }
+
+        [Fact]
+        public void Values_can_be_correctly_converted_to_nullable_TimeSpan_without_the_parser_specifying_a_custom_converter()
+        {
+            var timeSpanString = "30";
+            var option = new Option<TimeSpan?>("-x");
+
+            var value = option.Parse($"-x {timeSpanString}").GetValueForOption(option);
+
+            value.Should().Be(TimeSpan.Parse(timeSpanString));
+        }
+
         [Fact]
         public void Values_can_be_correctly_converted_to_Uri_without_the_parser_specifying_a_custom_converter()
         {

src/System.CommandLine/Binding/ArgumentConverter.StringConverters.cs

@@ -255,5 +255,17 @@ internal static partial class ArgumentConverter
             value = default;
             return false;
         },
+
+        [typeof(TimeSpan)] = (string input, out object? value) =>
+        {
+            if (TimeSpan.TryParse(input, out var timeSpan))
+            {
+                value = timeSpan;
+                return true;
+            }
+
+            value = default;
+            return false;
+        },
     };
 }