nixos-with-flakes

[Hayao0819]

• modularize-the-configuration.md (@Hayao0819 )
• get-started-with-nixos.md (@Hayao0819 )
• update-the-system.md (@CP-WD )
• other-useful-tips.md (@Hayao0819 )
• start-using-home-manager.md
• downgrade-or-upgrade-packages.md (@Hayao0819 )
• introduction-to-flakes.md (@rytst )
• nixos-with-flakes-enabled.md(@rytst )
• nixos-flake-and-module-system.md
• nixos-flake-configuration-explained.md

このディレクトリを優先的に翻訳していきたいです。