Use core version 2.8.0

[janedbal]

• diff: https://github.com/editorconfig-checker/editorconfig-checker/compare/2.7.0...2.8.0
• release notes:
  • https://github.com/editorconfig-checker/editorconfig-checker/releases/tag/2.8.0
  • https://github.com/editorconfig-checker/editorconfig-checker/releases/tag/2.7.2
  • https://github.com/editorconfig-checker/editorconfig-checker/releases/tag/2.7.1