Prevent immediate window restore from minimize in core_window_flags
The core_window_flags example automatically restores the window from
being minimized after 3 seconds. However, it only resets the frameCounter
if the window is minimized through the app from inputting KEY_N. This
means if you miminize the window by other means (like pressing the minimize
button) then the example will immediately restore the window because the
frame counter wasn't reset. I've fixed this by setting the frameCounter
back to 0 once it's expired. I also added a note in the UI that the example
automatically restores the window so it's not a surprise.