Change package ID to "packageurl-dotnet"

[ThomasPiskol]

Fixes the issue with an existing package ID from an unofficial package as described in #12.

Upload tested locally with our existing NuGet API Key:

dotnet nuget push "nuget/*.nupkg" --api-key $NUGET_API_KEY --source https://api.nuget.org/v3/index.json
Pushing packageurl-dotnet.0.1.8-test-upload.0.nupkg to 'https://www.nuget.org/api/v2/package'...
  PUT https://www.nuget.org/api/v2/package/
  Created https://www.nuget.org/api/v2/package/ 1017ms
Your package was pushed.
Pushing packageurl-dotnet.0.1.8-test-upload.0.snupkg to 'https://www.nuget.org/api/v2/symbolpackage'...
  PUT https://www.nuget.org/api/v2/symbolpackage/
  Created https://www.nuget.org/api/v2/symbolpackage/ 503ms
Your package was pushed.

And here's the result:

https://www.nuget.org/packages/packageurl-dotnet/

[ThomasPiskol]

After thinking about this I propose the to change the ID / name of our NuGet package to packageurl-dotnet.

Even if we can somehow manage to get ownership of the PackageUrl ID, it still might be confusing for existing users of that package and could introduce breaking change for them.

By using packageurl-dotnet we keep the GitHub repository name in sync with the NuGet package ID / name. This is also how it's currently done for Python (packageurl-python) and Javascript (packageurl-js).

@am11 @sschuberth What do you think?

[am11]

By using packageurl-dotnet we keep the GitHub repository name in sync with the NuGet package ID / name.

Makes sense. Discoverability is an important aspect. Go for it.