Optional fields are not supported

[ellik95]

Describe the bug
It seems that optional fields are not supported. In the target output the getters generators return the type of the field, but they need to return ${type} | undefined.

To Reproduce
Steps to reproduce the behavior:

Props ProjectProps {
  optional string name;
}

Expected behavior
The typescript output must be like below:

get name(): string | undefined {
    return this.props.name;
  }

Additional context
Check if there is other problem with optional and that everything works well.