Briefly explain horizontal scrolling in tutorial (#1065)

* Update README.md

Add note on horizontal scrolling

tutorials/Desktop_Components/README.md

@@ -90,6 +90,8 @@ fun TextBox(text: String = "Item") {
 }
 ```
 
+Scrollbars can be moved by dragging the bars and using the mouse wheel or the touchpad. Horizontal scrolling with the mouse wheel can be performed by side-clicking the whell or by holding down `Shift`.
+
 <img alt="Scrollbars" src="scrollbars.gif" height="412" />
 
 ## Lazy scrollable components with Scrollbar