Doesn't work with different field sizes

If a form field is using a different form size, other than "medium", then the str_replace() fails to change anything. Perhaps turn this into a regx to allow for small|medium|large ?

Look for the str_replace() call that applies Bootstrap classes to form fields. The issue mentions it fails for sizes other than 'medium'. Find where field sizes are defined in Gravity Forms and adjust the replacement to handle 'small', 'medium', 'large' via regex. Test with different field size settings to ensure classes are applied correctly.

索引モデルが issue の本文から書いたものです。