add --ipc for integration with Shotcut

I accomplished my goal for this integration! After running some experiments, I decided not to try to embed Glaxnimate as a so-called page or alternate mainwindow layout. There were a number of big problems to work through. As a separate window it can be very nice workflow especially if you have multiple monitors or a very large one. I have it working such that you can leave Glaxnimate open, and from Shotcut choose to open different animations on the timeline into the same Glaxnimate window. To get away from the build and runtime issues I experienced with embedding or in-process, I instead built out inter-process communication. It is working good to let Glaxnimate show video as the canvas background. Glaxnimate continues to be built separately, has its own executable, and its own process. This approach also keeps changes low and clean and maintainable.