Give mods access to imgui context

[GameParrot]

Allows mods to use imgui directly with ImGui::SetCurrentContext

[ChristopherHX]

Although this might read as a nice idea...

This is very very very very dangerous see git blame https://github.com/ocornut/imgui/blame/6982ce43f5b143c5dce5fab0ce07dd4867b705ae/imgui_internal.h#L2031-L2395C2

this struct is part of imgui internals and changes over time.

The whole struct layout get new items in the middle that moves other members in memory.

Doing this would stop updates of imgui in this launcher and for mods (this involves to remove the submodule updates for imgui), otherwise an unmaintainable change

Every mod must use a binary compatible snapshot of imgui, once the launcher bumps it mods are going to crash the process.