- Created event_manager global variable.
- Event broadcasting works. Lets see it shine.
- Added mouse_btn, char, and key GLFW callbacks to the event broadcasting.
- Base 2 event channel ids, to be able to combine them.
- Started (provisional?) main loop, base on shitty GLFW windowShouldClose.
- Created SYS_SUBSCRIBE macro, to easily subscribe a system to an event channel.