Handle rate limit 429

[greg-finley]

I observed that Quip returns 429 on rate limit exceeded. I failed to export my Quip docs several times but it worked after changing this line to handle both 429 and 503 the same way (though I don't think the API returns 503 for rate limits).

It should close #43

[bneutra]

Just a note on this: as of Dec 2023, I observe that quip returns both 503's and 429's and for 503's it correctly sets x-ratelimit-reset but for 429's it sets it to 0. So, I ended up special casing 429 and just setting the wait time to 61s, otherwise the client code doesn't regulate itself for 429's

[jspiro]

Here's a working workaround for this issue:
jspiro@837ef96

I've updated the README in that branch to help anyone wanting to run this. It will take A LOT longer to run, but it should complete and not miss any files.

$ npx "jspiro/quip-export" should do it.