Add support for urllib3

[stevepiercy]

urllib3 has surpassed Requests in downloads.

• https://pypistats.org/top
• https://urllib3.readthedocs.io/en/stable/index.html

Both Requests and pip depend on it.

[datakurre]

I could do this. Maybe all the previous work to keep building requests examples through AST tree finally pays off 😅