fix: do not lose focus when opening the side menu in the docs app

Now the focus moved to the 'close' button of the opened sidebar
TEST PLAN:
open and close the menu on the docs app with keyboard. Focus should not get lost. Also test with
screenreaders

Author: matyasf

packages/__docs__/src/App/index.tsx

@@ -613,6 +613,11 @@ class App extends Component<AppProps, AppState> {
               shape="circle"
               color="secondary"
               size="medium"
+              ref={(button) => {
+                if (button) {
+                  button.focus()
+                }
+              }}
             />
           </InstUISettingsProvider>
         </View>