build: push nuget package to github registry

[sanzoghenzo]

I've messed up with my remotes and pushed directly in this repo, but that turned out to be a good thing since I already tested that the CI works!

You can see the package in the Packages section of the organization

Should we constrain the upload to specific branches? pyrevit-main? pyrevit-5-main?

[sanzoghenzo]

@dosymep care to take a look at this? 4 eyes are better than 2 😉

I've added the constraint to package and push the package only on pyrevit-main and pyrevit-5-main, and skip the duplicates so that the ci doesn't errors out if we try to push a package with the same version.