Adds mqtt example

[robmarkcole]

As title. My editor black formatted the setup.py, hope thats OK

[Gadgetoid]

Thank you. I tweaked the example to better handle Ctrl+C - it was stalling for me since the global scope running variable was shadowed by the local scope in main().

I've also reverted setup.py because it throws an error when I try to run it- example dependencies don't need to be included in the library, anyway.