Doesn't seem to crash with fonts now, but can't find the renderer plugin?

Per-context IOs all over the place, but font loading is failing :(

Start working on a per-PIXI-DisplayObject context renderer for ImGui

Bring in the packaged UMD export of pixi.js from our own repo

Moved the impl to the src/ folder so I can start working on a proper PIXI ImGui implementation (probably with render-to-texture)