PixiJS v8 migration

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Pixi.js is preparing to release v8 and is in beta now.. It will include a lot of breaking changes, but also some cool features like performance improvements and support for WebGPU.

This is just an issue to track that we should migrate to v8 once it's stable and we have the time to do so.

More info: https://github.com/pixijs/pixijs/releases https://github.com/pixijs/pixijs/discussions/9791