Update net100.md (#2124)

fixed typo

Author: mghini

dotnet-desktop-guide/winforms/whats-new/net100.md

@@ -40,7 +40,7 @@ SnapLines were fixed for custom designers.
 
 ## Dark mode
 
-Windows Forms for .NET 9 introduced preliminary dark mode visual styling, with the goal of completing impelmentation in .NET 10.
+Windows Forms for .NET 9 introduced preliminary dark mode visual styling, with the goal of completing implementation in .NET 10.
 
 - `ListView` column headers are now working.
 - `StatusStrip` and `ToolStrip` render correctly.