Updated release notes

Author: gigi81

ReleaseNotes.md

@@ -1,3 +1,9 @@
+22.0.0
+- (Breaking) Removed support for some Async calls in .NET Framework and legacy versions of .NET to better support .NET 8 and later
+- Minimum required TestableIO.System.IO.Abstractions version is now 22.x
+- Removed .NET 7 build (should still work with .NET standard build)
+- Removed .NET 6 build (should still work with .NET standard build)
+
 2.0.0
 - (Breaking) Moved all extensions methods to 'System.IO.Abstractions' namespace
 - Added ThrowIfNotFound extension methods