Links for the "Further Reading" chapter

[slevithan]

Thanks for the great book, Sundeep!

For the Further Reading page, I have a couple suggestions:

• The Regex+ library.
• I'd recommend updating the "Awesome Regex" link to point to https://github.com/slevithan/awesome-regex
  • This is a newer collection. The older page that's currently linked seems to no longer be actively maintained, and it includes a lot of dead links that now point to spam sites, along with a lot of suboptimal links to tools and resources that are not best in class.