Correct a typo in Converters.ToFileSizeString and add unit tests

CommunityToolkit.Common/Converters.cs

@@ -42,7 +42,7 @@ public static string ToFileSizeString(long size)
         }
         else
         {
-            return ((size >> 50) / 1024F).ToString("F0") + " EB";
+            return ((size >> 50) / 1024F).ToString("F1") + " EB";
         }
     }
 }

tests/CommunityToolkit.Common.UnitTests/Test_Converters.cs

@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace CommunityToolkit.Common.UnitTests;
+
+[TestClass]
+public class Test_Converters
+{
+    [TestMethod]
+    [DataRow(1024L - 1, "1023 bytes")]
+    [DataRow(1024L, "1.0 KB")]
+    [DataRow(1024L * 1024, "1.0 MB")]
+    [DataRow(1024L * 1024 * 1024, "1.0 GB")]
+    [DataRow(1024L * 1024 * 1024 * 1024, "1.0 TB")]
+    [DataRow(1024L * 1024 * 1024 * 1024 * 1024, "1.0 PB")]
+    [DataRow(1024L * 1024 * 1024 * 1024 * 1024 * 1024, "1.0 EB")]
+    public void Test_ToFileSizeString(long size, string expected)
+    {
+        Assert.AreEqual(expected, Converters.ToFileSizeString(size));
+    }
+}