Added X1 & X2 Mouse Buttons to Windows

[KalevGonvick]

You can use MOUSEEVENTF_XDOWN or MOUSEEVENTF_XUP and specify the button number in the mouseData field to pick which button you want to use.

I found this info in the docs on this page here: https://learn.microsoft.com/en-us/windows/win32/api/winuser/ns-winuser-mouseinput