Add Steam+DpadUP binding (#8)

* Add Steam+DpadUP binding [ci skip]

Windows on SteamDeck generally needs a hotkey available to use with upscaling applications as many games crash when attempting to render exclusive fullscreen.

Added the following binding:
- Steam + DPadUP = Ctrl+Alt+U

* Include new Steam+DPadUP binding in readme

Added keybind to table list. Included instructions on how the binding can be used to set up a full screen scaling toggle.

SteamController/Profiles/DefaultGuideShortcutsProfile.cs

@@ -103,6 +103,11 @@ namespace SteamController.Profiles
             {
                 c.Keyboard.KeyPress(VirtualKeyCode.ESCAPE);
             }
+            
+            // Additional binding for tool hotkeys (Lossless Fullscreen is nice)
+            if (c.Steam.BtnDpadUp.HoldOnce(ShortcutConsumed)) {
+                c.Keyboard.KeyPress(new List<VirtualKeyCode> { VirtualKeyCode.LCONTROL, VirtualKeyCode.LMENU }, VirtualKeyCode.VK_U);
+            }
         }
 
         protected void EmulateScrollOnLPad(Context c)