Pack repository as an UPM package

UPM packages are a great way to easily install Unity packages with only two clicks in the Package Manager and pasting the link to the repository. It comes with automatic update and dependencies systems, plus you don't have to drag the source code directly to your `Assets` folder.

I think packing this tools as an UPM package would be great, since I'm planning to use this on several different projects and UPM packages are the most organized way of managing plugins.

I've packed my own UPM packages before, so, would you be okay with a pull request doing exactly that? (Take into account that manually importing the asset would still be possible).