Allow for API usage with customization/extensions

[rosskevin]

First, this is awesome, not just this project but related works.

Is this repo effectively abandoned? I see that there are a lot of outstanding PRs and issues.

I note that instance arg does not work properly on the latest npm verison, and the web project uses an older version of this dependency. I also note bugs like duplicate types being generated.

A fact of where we are with our own project is that we expect our complex models to be continually iterated upon which means we need to regenerate on a consistent basis. With our effort to build a configurator, each regeneration will set us back each time unless we have some broad-strokes control/pluggability of the jsx generation.

I would like to customize the jsx generation, first and specifically the <mesh> output to better accommodate custom colors. /related #257

TL;DR I see many issues and PRs filed, with no response. Is the project open to help or is this effectively abandoned?

[rosskevin]

PR available #286

[rosskevin]

Temporary fork published: https://github.com/rosskevin/gltfjsx @rosskevin/gltfjsx

I hope this is a temporary package and https://github.com/pmndrs/gltfjsx/pull/286 is accepted, but I've got to move on and start using it in a production/published environment.