Add flake8 testing on github actions

[hmaarrfk]

@colinoflynn could you create a token on pypi.org for picoscope then add it to this repository as a secret on github called

PYPI_API_TOKEN

thanks!

I think we also talked about upping my privilidges once, but we never pulled the trigger on it.

[hmaarrfk]

The API token creation should look like:

[hmaarrfk]

Kind ping for @colinoflynn

[colinoflynn]

Done - let me know if that works!