feat: add support for new potree format

[MPanknin]

This PR adds support for the new Potree format 2.0 aka metadata.json.

It is based to a large extent on this community fork https://github.com/shiukaheng/potree-loader and on https://github.com/tentone/potree-core as well as https://github.com/potree/potree obviously.

Main differences being:

• We stick with WebPack rather then swicthing to Parcel or Vite
• Removed the support for brotli decoding because embedding the complete library feels unnatural. Brotli decoding should be based on https://github.com/foliojs/brotli.js as dependency. Scope of another PR
• We stick with our current shader model rather than upgrading to #version 300 es. If we really need this at some point it should be scope of another PR since all the refactoring clutters the actual update.
• Tried to obey our conventions for file names
• Preserves our code for screen space clipping

[turien-pix4d]

For an example, it would probably feel more natural to check if the url is loaded rater than the version

[MPanknin]

Thanks for the suggestions @turien-pix4d I've updated the unloading accordingly. In terms of checking the url, I personally think we can leave it as is as this is really just meant as an example to show how to load and dump the two different Pointcloud versions.