共通フォルダ「common」を追加

テストもかねて
Revert "共通フォルダ「common」を追加"

This reverts commit dd9159f52ad51dd32644c8a4af5cea95e8390709.
Revert "Revert "共通フォルダ「common」を追加""

This reverts commit 35099d65f29afa897ebaef7fb91549c04f707d00.