puppeteer example

[puppeteer](https://github.com/puppeteer/puppeteer) is popular for screenshot usage

I think that almost example has SSRF vulnerbility.

- [Create a website screenshot service with Puppeteer on Heroku - Fabio Franchino](https://fabiofranchino.com/blog/create-website-screenshot-service-with-puppeteer-on-heroku/)
- [Save screenshot of websites with Puppeteer, Cloudinary and Heroku with Node.js](https://medium.com/@viviancpy/save-screenshot-of-websites-with-puppeteer-cloudinary-and-heroku-1-3-bba6082d21d0)
- [How to take screenshots using Puppeteer - Dishant Agnihotri - Medium](https://medium.com/@dishantagnihotri/how-to-take-screenshots-using-puppeteer-79d18157ed0d)

If puppeteer support `http.Agent`, it is reasonable to add the example code in README.
If puppeteer does not support `http.Agent`, that is out of scope.

Start by reading README.md and checking whether Puppeteer supports an http.Agent for screenshot requests. Confirm whether the linked screenshot patterns can be protected from SSRF; done means adding a README example if supported, or documenting that the request is out of scope if it is not.

Written by the indexing model from the issue text.