Better Handling for Missing `states` Files

Use `array_replace_recursive` or `array_merge_recursive` to merge
default placeholder data with user-defined data.
Fix Grammar –S

Configuration ← Fix this!
Articles
Pages
Comments
Tags
Menu ← Fix this!
Assets
Fields
Shortcodes
Shields
Plugins
Cache ← Fix this! Is this correct? → “Caches”
Backup ← It is okay