Function optional

optional<T extends BSBType>(type: T): T & { optional: true }
Mark a type as optional. Optional fields are not required in object schemas.
Type Parameters
- T extends BSBType
Parameters
- type: T
Returns T & { optional: true }
Example
```
const UserSchema = bsb.object({
  name: bsb.string(),           // Required
  bio: optional(bsb.string()),  // Optional
});
```
- Defined in src/interfaces/schema-types.ts:539