Fix typo in code sample (#447)

Author: Scanerrr

app/ng-ui-widgets-category/switch/styling/article.md

@@ -1,6 +1,6 @@
 The styling properties for the `Swtich` control are as follows:
 - `color`- Controls the handle color
-- `bacxgroundColor`(`background-color` in CSS) - Controls the background color while the switch is in **ON** state.
+- `backgroundColor`(`background-color` in CSS) - Controls the background color while the switch is in **ON** state.
  - `offBackgroundColor` (`off-background-color` in CSS) - Controls the background color while the switch is in **OFF** state.
 
 <snippet id='switch-styling-html'/>