/learning page - several external links broken

[raswonders]

Hi, while reading through /learning I found some dead links.

I've ran linkinator against the page and found little more. I'd gladly help fixing these with PR, if you assign me the issue.

STATUS           URL
404      https://sdras.github.io/object-explorer/
0        https://javascript.pythoncheatsheet.org/
0        https://internetingishard.com/html-and-css/
404      https://nodejs.dev/en/learn/an-introduction-to-the-npm-package-manager
404      https://nodejs.dev/en/learn/how-to-install-nodejs      
410      https://blog.bitsrc.io/a-beginners-guide-to-regular-expressions-regex-in-javascript-9c58feb27eb4
404      https://formidable.com/blog/category/redux-saga/       
404      https://medium.freecodecamp.org/a-comprehensive-guide-to-react-js-in-2018-ba8bb6975597
404      https://greensock.com/react-advanced

[markerikson]

We don't typically worry about "assigning", but yes, PRs to update those are greatly appreciated!