Add an option to skip 429

[ai]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and discussions and couldn’t find anything (or linked relevant results below)

Problem

Some servers see that I am making too many requests and return 429 sometimes:

README.md
239:54-239:96 warning Unexpected dead URL `[https://npmgraph.js.org/`](https://npmgraph.js.org/%60), expected live URL                    no-dead-urls remark-lint
  [cause]:
              error   Unexpected not ok response `429` (`Too Many Requests`) on `[https://npmgraph.js.org/`](https://npmgraph.js.org/%60) dead         dead-or-alive

Current solutions

Ignore the whole URL which is hard (many of them can return 429

Proposed solutions

Add option ignore429

[wooorm]

Hey Andrey! 👋

Do you know if those URLs return Retry-After headers?
Ref #56 (comment)