enhancement: added proxy pattern known use (iluwatar#2507) (iluwatar#2554)

Author: thestbar

Diff for: proxy/README.md

@@ -157,6 +157,7 @@ Typically, the proxy pattern is used to
 * [Apache Commons Proxy](https://commons.apache.org/proper/commons-proxy/)
 * Mocking frameworks [Mockito](https://site.mockito.org/), 
 [Powermock](https://powermock.github.io/), [EasyMock](https://easymock.org/)
+* Apple UIKit's [UIAppearance](https://developer.apple.com/documentation/uikit/uiappearance)
 
 ## Related patterns