Update Release Notes in csproj file to point to release notes on GitHub

[darrelmiller]

Rather than duplicating release notes in the csproj and on GitHub, we should add a link to the GitHub Releases page for this repo into the csproj release notes. I recommend just pointing to e.g https://github.com/microsoft/OpenAPI.NET/releases/tag/1.3.3 We can update the version each time we update the library version in the csproj.