Update imguifilesystem.cpp
Update imguifilesystem.cpp

Added windows.h to make it easier to compile as stand-alone. See https://github.com/Flix01/imgui/issues/13.
wflohry/imgui-addons,tom-seddon/imgui,Flix01/imgui,Flix01/imgui,Flix01/imgui,wflohry/imgui-addons,tom-seddon/imgui