update change log

Author: daveMueller

Documentation/Changelog.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Unreleased
 
 ### Fixed 
+-Fix summary output format for culture de-DE [#1263](https://github.com/coverlet-coverage/coverlet/issues/1263)
 -Fix threshold doesn't work when coverage empty [#1205](https://github.com/coverlet-coverage/coverlet/issues/1205)  
 -Fix branch coverage issue for il switch [#1177](https://github.com/coverlet-coverage/coverlet/issues/1177)  
 -Fix branch coverage with using statement and several awaits[#1176](https://github.com/coverlet-coverage/coverlet/issues/1176)  

test/coverlet.core.tests/Helpers/FormatHelperTests.cs

@@ -10,10 +10,13 @@ public class FormatHelperTests
         [InlineData(2.2d, "2.2")]
         public void TestInvariantFormattableString(double number, string expected)
         {
+            var currentCulture = Thread.CurrentThread.CurrentCulture;
             Thread.CurrentThread.CurrentCulture = new CultureInfo("de-DE");
+            
             var actual = new FormatHelper().Invariant($"{number}");
 
             Assert.Equal(expected, actual);
+            Thread.CurrentThread.CurrentCulture = currentCulture;
         }
     }
 }