bug: falsy directive args are dropped

[elijaholmos]

When supplying a falsy argument to a custom directive, the argument is omitted from the generated schema.

Sample GQL: (with codgen config from https://github.com/Code-Hex/graphql-codegen-typescript-validation-schema/blob/main/codegen.yml)

input EventArgumentInput {
  name: String! @constraint(minLength: 0)
  value: String! @constraint(startsWith: "foo")
}

directive @constraint(
  minLength: Int
  startsWith: String
) on INPUT_FIELD_DEFINITION | FIELD_DEFINITION

Expected Schema Output:

export function EventArgumentInputSchema(): yup.SchemaOf<EventArgumentInput> {
  return yup.object({
    name: yup.string().defined().min(0),
    value: yup.string().defined().matches(/^foo/)
  })
}

Actual Schema Output:

export function EventArgumentInputSchema(): yup.SchemaOf<EventArgumentInput> {
  return yup.object({
    name: yup.string().defined().min(), // <-- "Expected 1-2 arguments, but got 0. ts(2554)"
    value: yup.string().defined().matches(/^foo/)
  })
}

I intend on submitting a PR to resolve this issue.

[Code-Hex]

@elijaholmos Thanks for your PR!
I just published a new version which is contained your fixes.

https://github.com/Code-Hex/graphql-codegen-typescript-validation-schema/tree/v0.6.2

Thank you!