Create UPM format branch

[Danil0v3s]

This is the branch I've created to prove the concept of UPM

Note: this is still using a separate source for DotRecast which I still think is the best option

As I think merging this will not be possible, here's a gist for you to follow:

Inside a random project's Packages folder, create a folder with a package name, like this

Fill the package.json with this info and change accordingly:

{
    "name": "com.defnotagamestudio.unirecast",
    "displayName": "UniRecast",
    "version": "0.0.1",
    "unity": "2022.3",
    "description": "ikpil's UniRecast made as a Unity library",
    "keywords": [],
    "category": "",
    "author": {
      "name": "Definitely Not a Game Studio",
      "email": "daniloleemes@hotmail.com",
      "url": "https://github.com/def-not-a-game-studio"
    },
    "repository": {
      "type": "git",
      "url": "https://github.com/def-not-a-game-studio/UniRecast.git",
      "directory": "com.defnotagamestudio.unirecast"
    }
  }

After that you can start moving the code around, I've created a few assembly definitions but I think these could be reduced.

Sorry for the many files changed, my IDE automatically organize imports.

Another alternative would be if you checked out my branch and pushed it to the main repo

[ikpil]

thanks!