chore: update doc/controls/ShadowContainer.md

Co-authored-by: Agnès ZITTE <16295702+agneszitte@users.noreply.github.com>

doc/controls/ShadowContainer.md

@@ -11,7 +11,7 @@ A reference to [Uno.Toolkit.Skia.WinUI](https://www.nuget.org/packages/Uno.Toolk
 ## Remarks
 Currently, the control simply mimics the shape of its content by size and by corner radius. Complicated shapes, such as text or pictures with alpha, are not yet supported.
 
-In order for inset (inner) shadows to be paint on top of background, the `ShadowContainer`'s child element should not have a `.Background` or `.Fill`(for `Shape`s), it should be omitted or set to transparent. And, the background/fill value should be instead set on the `ShadowContainer` itself.
+In order for inset (inner) shadows to be painted on top of the background, the `ShadowContainer`'s child element should not have a `.Background` or `.Fill`(for `Shape`s), it should be omitted or set to transparent. And, the background/fill value should be instead set on the `ShadowContainer` itself.
 ```xml
 <!-- DO -->
 <utu:ShadowContainer Background="..." Shadows="...">