feat: VPM listing

[lillithkt]

A working listing is up at https://imlvna.github.io/UdonToolkit/

Merging this PR and enabling github pages will put a listing at https://orels1.github.io/UdonToolkit whenever you release a version

[orels1]

Hey! Thanks for all the work you did repackaging the toolkit! I really appreciate it. I been slowly chipping away at transitioning everything to proper packages over here on next branch. Its not fully ready yet, but it should be pretty stable.

I tried to keep the asmdefs in the same sports so the references are intact, but its now split into:

• UdonToolkit package (all the misc behaviours and such)
• UdonToolkit Inspector package (all of the things that were in "internal" are now there, and it uses the old UdonToolkitEditor and UdonToolkitRuntime asmdefs to keep things referenced correctly)
• UdonToolkit Flight System
• UdonToolkit Presentation System

Since the latter two are completely standalone - they were also separated, making the inspector and main toolkit packages very small

[orels1]

You can check out the new listing here: https://orels1.github.io/UdonToolkit/index.json

The packages are currently marked as 2.0.0-dev.1 pre-release