breaking: rewrite assetpack

[Zyie]

This PR is a complete overhaul of AssetPack to simplify its design and provide some new powerful features

• Caching now works! AssetPack will only transform an asset when it changes
• Supports multipacked spritesheets
• Supports compressing spritesheets and atlas files to webp/avif
• Added cache busting strings to filenames
• A complete set of docs with examples for how to set up the project
  https://pixijs.io/assetpack/
• Remove monorepo design, you now only need to install @assetpack/core

[GoodBoyDigital]

Code wise, this is all good! As we have had heavy reviews on this internally as we developer it.

Docs wise. Here is my feedback:

• lets put the examples at the top of each page, above the API!
• A configurable asset pipeline for web games -> A configurable asset pipeline for the web

• i wander if we remove the cahce-busting in the result image? Might make it easier to understand! ]

,

• for the manifest section, lets so the manifest thats generated. I think its worth showing some code on how this can be used in Pixi too via Assets!

Great work man!