Rebrand demo script

[juanmc2005]

Problem

The demo script is useful not only as a demo but also as the default way to quickly run the pipeline and see how it behaves under different scenarios. I feel like it's wrong to call it a "demo".

Idea

Change the name from "demo" to "stream", which also reads more clearly:

python -m diart.stream microphone
python -m diart.stream some_file.wav

It would also be useful to improve the argument documentation, since some information is missing, like default values.

[juanmc2005]

Implemented in PR #47