qr_code model is missing "pages" attribute

[unclejustin]

Summary

As per https://docs.lob.com/#tag/Letters/operation/letter_create qr_code allows for a "pages" attribute to determine what page to render the qr code. This is missing from the model.

Expected Behavior

Should allow "pages" for qr_code.

Current Behavior

Typescript error will not allow "pages".

Possible Solution

Add pages/: string to qr_code model.

Steps to Reproduce

1. Try to use pages as an attribute for qr_code when creating a letter.
2. Open an issue about how this doesn't work 😂

Context (Environment)

I am trying to create a letter using the sdk.