Use Github actions to automate the release process

[martinbryant]

• Add a Github action that is triggered on Github release
• Automation of release notes process that is generated using the PR's merged since last release
• Version is driven from the version in the Github release
• Release notes in the Nuget package is now a link to the Github release notes
• Nuget push now is done on the build machine only - prevents commits being done programatically
• Nuget secret is now a secret on the repository
• The template proj file using up to date constructs for licence, readme and logo

[Larocceau]

@martinbryant Looks good, except that I thought we agreed on keeping the push in the to nuget in build script, since GH automatically hides them? https://docs.github.com/en/actions/security-guides/using-secrets-in-github-actions#redacting-secrets-from-workflow-run-logs