[ts] Allow making screen params optional

[janicduplessis]

When defining the type for ParamsList it is not possible to make passing parameters optional. It is only possible to have no parameters at all or some.

Here are some examples to demonstrate:

type RootStackParamsList = {
  screen: undefined,
  screenWithParams: {a: string},
  screenWithOptionalParams: {a?: string} | undefined,
}

navigate('screen') // OK
navigate('screenWithParams', {a: 'a'}) // OK
navigate('screenWithParams') // errors OK
navigate('screenWithOptionalParams', {a: 'a'}) // OK
navigate('screenWithOptionalParams', {}) // OK
navigate('screenWithOptionalParams') // errors but should work.

This means that if screen params are {} | undefined we should allow not passing any parameter to navigate for this screen.