Feature Request: allow non-pointer Go types on optional fields in TS

[chaofz]

Hi,

Thanks for making this awesome tool! I have a feature request for the conversion from TS to Go. I wonder if it makes sense to add an option not to convert TS optional fields to Go pointer types.
I make this request because Go already treats all struct fields optional and drops empty with omitempty tag in JSON serialization.

For example
TS:

class Contact {
  firstName: string;
  lastName?: string;
}

Current state on converting to Go:

type Contact struct {
	FirstName string       `json:"firstName"`         
	LastName *string       `json:"lastName,omitempty"`
}

Proposed change:

type Contact struct {
	FirstName string      `json:"firstName"`         
	LastName string       `json:"lastName,omitempty"`
}