feature: tcort side just support `retry` for 429 error

[Yiyiyimu]

Thank you for your help! This repo is so helpful.

This feature is just supported in tcort/markdown-link-check#106 and others urged it in #56 . Hope it could be also supported on this side.

[Yiyiyimu]

It seems not a problem, we could add it into config.json. My mistake, close.