Capture keyboard and mouse for ImGui

[cesarl]

Regarde, y a ca dans imgui pour pas que quand on tape des queutrus dans imgui l'engine les interprete lui aussi.

IMGUI_API void          CaptureKeyboardFromApp();                                           // manually enforce imgui setting the io.WantCaptureKeyboard flag next frame (your application needs to handle it). e.g. capture keyboard when your widget is being hovered.
IMGUI_API void          CaptureMouseFromApp();                                              // manually enforce imgui setting the io.WantCaptureMouse flag next frame (your application needs to handle it).