[Documentation improvement request] A beginner-friendly small real use case code example

[simon-liebehenschel]

The existing documentation is abstracted away from real world with code snippets of "blinker" interface usage.

If you will take a look at some other packages documentation, you may find that there are nice small real usage example. E.g. take a look at aiohttp documentation > getting started.

It will be great if "blinker" will have a small real code example included.

Thank you.