Bug: If a capture group is part of an optional parent group it is not marked as optional

Current:
```ts
const regex = TypedRegEx("^\w+(@(?<version>[a-z0-9-_.]+))?$", "gi");
const captures = regex.captures(...); // { version: string } | undefined;
```

Expected:
```ts
const regex = TypedRegEx("^\w+(@(?<version>[a-z0-9-_.]+))?$", "gi");
const captures = regex.captures(...); // { version?: string | undefined } | undefined;
```