Hi @hiroshi
If you want to create a new add-on (plugin), please check this page: https://codex.wordpress.org/Writing_a_Plugin.
I’m afraid ACF doesn’t have a tutorial to create ACF add-on. But if you want to create a new field type like “child terms” (only shows child terms), for example, you can follow this guide: https://www.advancedcustomfields.com/resources/creating-a-new-field-type/.
I hope this helps 🙂