The out of scope variable: mention `nonlocal`

[actionless]

https://github.com/satwikkansal/wtfpython#-the-out-of-scope-variable

To modify the outer scope variable a in another_func, use global keyword.

https://docs.python.org/3/reference/simple_stmts.html#grammar-token-nonlocal-stmt

[diptangsu]

I would love to add this to this repo!

[satwikkansal]

Sure @diptangsu, Feel free to submit a PR for this.

[diptangsu]

I have submitted a PR. I also made some extra changes. Let me know if I need to change something, I'll add the required changes and add another commit!

[satwikkansal]

Thank you @diptangsu for going beyond just mentioning nonlocal and adding a nice example for it. Really appreciate it :)