Suggestion: Add function that returns position and size of a window

[SirRFI]

Suggestion: Add function that returns position (X, Y) and size (width, height) of a window.

Example:

hwnd := robotgo.FindWindow("Notepad")
x, y := robotgo.GetWindowPosition(hwnd) // int, int or robotgo.Point
w, h := robotgo.GetWindowSize(hwnd) // int, int or robotgo.Size
rect := robotgo.GetWindowRectangle(hwnd) // probably needs better name; robotgo.Rect