Function ROptional

ROptional<T extends TSchema>(schema: T): TROptional<T>
Creates a schema for optional values (value or null).

Wraps any schema to allow null in addition to the normal type. The codec uses the wrapped schema's type code and handles null encoding/decoding.
Type Parameters
- T extends TSchema
Parameters
- schema: T
  The schema to make optional
Returns TROptional<T>
A Relish schema accepting T or null
Example
```
import { ROptional, RString, createCodec } from '@grounds/schema';

const schema = ROptional(RString());
const codec = createCodec(schema);

codec.encode('hello').match(
  (bytes) => console.log('Encoded string:', bytes),
  (error) => console.error(error)
);

codec.encode(null).match(
  (bytes) => console.log('Encoded null:', bytes),
  (error) => console.error(error)
);
```
Remarks
Preserves the wrapped schema's type code for efficient encoding.
See
- RNull for null-only values
- field for optional struct fields