Github repo setup

[weichch]

This issue is used to track the tasks to setup for this repository.

• [x] Move benchmarks out of Readme.md
• [x] Add release notes
• [ ] Add contributing docs
• [ ] Add various templates, e.g. issue template
• [ ] Add Github actions and PR checks
  • [x] Add to run on ubuntu-latest for .NET and .NET Core
  • [ ] Add to run on windows-latest (or appropriate) for .NET Framework
• [x] Add build status to Readme.md
• [x] Add CODEOWNERS file and restrict PR approval access
• [ ] Add Wiki