2020 update

• update minimum required chef version to 15.0 (BREAKING CHANGE)
• update metadata.rb with new contents
• update attributes + recipe files with style fixes
• update changelog, contributing, readme and testing
• add GitHub templates for bugs and pull requests
• add GitHub Actions for linting and kitchen test
• add Codeowners
• add kitchen configs for ec2, dokken, vra
• rename .kitchen files to kitchen
• remove .ruby-version