Sharing IO structures

[Name-hw]

Looking at the current code, the original ImGuiIO can be controlled through functions, not structures, in Zig. However, when using ImGui, you may encounter situations where bit operations cannot be performed using only the functions implemented in Zgui. So there are two ways.

1. Share the io structure with zgui.io.getIo(). It is a different direction from what we have made so far, but it is an easy method.
2. Create a function corresponding to each member of the structure in zgui.io. (Current method)

[Name-hw]

@hazeycode

[hazeycode]

Why not both?

[Name-hw]

Because I guess there must be a specific reason why it was ported the way it is now.