feat: add get fieldNames method.
feat: add get fieldNames method.

bcit-ci/CodeIgniter4,kenjis/CodeIgniter4,bcit-ci/CodeIgniter4,kenjis/CodeIgniter4,bcit-ci/CodeIgniter4,bcit-ci/CodeIgniter4,kenjis/CodeIgniter4,bcit-ci/CodeIgniter4,kenjis/CodeIgniter4,kenjis/CodeIgniter4