Added spine debug visualizer demos

[miltoncandelero]

This is stuck behind a new version of @pixijs/spine (pixijs-userland/spine#453)

You can still pull this branch and test as it has a new dev build of pixi-spine

[bigtimebuddy]

Hey @miltoncandelero, I'm trying to work through all these remaining PRs. We are officially retiring this repo and redirecting to https://pixijs.com/examples
If you want to make this example available, you can do it over there:
https://github.com/pixijs/pixijs.com/tree/main/src/data/examples