adds protocol key to scan

[naveedhd]

It is required in my project. Might be useful for somebody else too.

Reported in #96.

[rockymeza]

Hi @naveedhd,

Thanks for adding this! Can you add to the tests for this? You can model them after https:/rockymeza/wifi/blob/master/tests/test_parsing.py

[naveedhd]

Hi @rockymeza, thanks for your response.

I have added the test for protocol in test_parsing.