add `WS_EX_TOOLWINDOW` in extended windows styles for GlosSI-Target

https://learn.microsoft.com/en-us/windows/win32/winmsg/extended-window-styles

Goal is to remove GlosSI-Target window in Alt-Tab listing as it will induce issues with Steam Link and not particularly intuitive when switching from and to a game.

Currently untested, PR needed only for building a PoC of it and checking for possible issues

GlosSITarget/TargetWindow.cpp

@@ -335,6 +335,10 @@ void TargetWindow::createWindow()
     style &= ~WS_OVERLAPPED;
     style |= WS_POPUP;
     SetWindowLong(hwnd, GWL_STYLE, style);
+    
+    auto exStyle = GetWindowLong(hWnd, GWL_EXSTYLE);
+    exStyle |= WS_EX_TOOLWINDOW;
+    SetWindowLong(hWnd, GWL_EXSTYLE, exStyle);
 
     MARGINS margins;
     margins.cxLeftWidth = -1;