fix: add isSortable to SmartFieldOptions type

[gventuri]

Definition of Done

I added isSortable to type SmartFieldOptions. It is a valid param for a field, and should be accepted by typescript (check it out here: https://github.com/ForestAdmin/forest-express/blob/main/src/services/apimap-fields-formater.js).

General

• [x] Write an explicit title for the Pull Request, following Conventional Commits specification
• [x] Test manually the implemented changes
• [x] Validate the code quality (indentation, syntax, style, simplicity, readability)
• [x] Ensure that Types have been updated according to your changes (if needed)

Security

• [x] Consider the security impact of the changes mad