… state

1. Update the form state comparison by converting numeric string fields to numbers, enabling correct dirty state evaluation
2. Add isNumericString utility function to identify numeric strings and exclude empty strings

Fixes: Shopify#2629

1. Add tests to ensure isNumericString() returns true for valid numeric strings
2. Add tests to ensure isNumericString() returns false for non-numeric strings
3. Add tests to ensure isNumericString() returns false for non-string values

Fixes: Shopify#2629